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  • 1.
    Asfaw, Habtom D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Valvo, Mario
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Maibach, Julia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ångström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tai, Cheuk-Wai
    Bacsik, Zoltan
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Boosting the thermal stability of emulsion–templated polymers via sulfonation: an efficient synthetic route to hierarchically porous carbon foams2016In: ChemistrySelect, ISSN 2365-6549, Vol. 1, no 4, p. 784-792Article in journal (Refereed)
    Abstract [en]

    Hierarchically porous carbon foams with specific surface areas exceeding 600 m2 g−1 can be derived from polystyrene foams that are synthesized via water-in-oil emulsion templating. However, most styrene-based polymers lack strong crosslinks and are degraded to volatile products when heated above 400 oC. A common strategy employed to avert depolymerization is to introduce potential crosslinking sites such as sulfonic acids by sulfonating the polymers. This article unravels the thermal and chemical processes leading up to the conversion of sulfonated high internal phase emulsion polystyrenes (polyHIPEs) to sulfur containing carbon foams. During pyrolysis, the sulfonic acid groups (-SO3H) are transformed to sulfone (-C-SO2-C-) and then to thioether (-C−S-C-) crosslinks. These chemical transformations have been monitored using spectroscopic techniques: in situ IR, Raman, X-ray photoelectron and X-ray absorption near edge structure spectroscopy. Based on thermal analyses, the formation of thioether links is associated with increased thermal stability and thus a substantial decrease in volatilization of the polymers.

  • 2.
    Borisov, Vladislav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Xu, Qichen
    KTH Royal Inst Technol, AlbaNova Univ Ctr, Sch Engn Sci, Dept Appl Phys, SE-10691 Stockholm, Sweden.;KTH Royal Inst Technol, SeRC Swedish Sci Res Ctr, SE-10044 Stockholm, Sweden..
    Ntallis, Nikolaos
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Clulow, Rebecca
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Shtender, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Cedervall, Johan
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden..
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Wikfeldt, Kjartan Thor
    KTH Royal Inst Technol, PDC Ctr High Performance Comp, SE-10044 Stockholm, Sweden..
    Thonig, Danny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Pereiro, Manuel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Bergman, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Delin, Anna
    KTH Royal Inst Technol, AlbaNova Univ Ctr, Sch Engn Sci, Dept Appl Phys, SE-10691 Stockholm, Sweden.;KTH Royal Inst Technol, SeRC Swedish Sci Res Ctr, SE-10044 Stockholm, Sweden..
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Tuning skyrmions in B20 compounds by 4d and 5d doping2022In: Physical Review Materials, E-ISSN 2475-9953, Vol. 6, no 8, article id 084401Article in journal (Refereed)
    Abstract [en]

    Skyrmion stabilization in novel magnetic systems with the B20 crystal structure is reported here, primarily based on theoretical results. The focus is on the effect of alloying on the 3d sublattice of the B20 structure by substitution of heavier 4d and 5d elements, with the ambition to tune the spin-orbit coupling and its influence on magnetic interactions. State-of-the-art methods based on density functional theory are used to calculate both isotropic and anisotropic exchange interactions. Significant enhancement of the Dzyaloshinskii-Moriya interaction is reported for 5d-doped FeSi and CoSi, accompanied by a large modification of the spin stiffness and spiralization. Micromagnetic simulations coupled to atomistic spin-dynamics and ab initio magnetic interactions reveal the spin-spiral nature of the magnetic ground state and field-induced skyrmions for all these systems. Especially small skyrmions similar to 50 nm are predicted for Co0.75Os0.25Si, compared to similar to 148 nm for Fe0.75Co0.25Si. Convex-hull analysis suggests that all B20 compounds considered here are structurally stable at elevated temperatures and should be possible to synthesize. This prediction is confirmed experimentally by synthesis and structural analysis of the Ru-doped CoSi systems discussed here, both in powder and in single-crystal forms.

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  • 3.
    Caron, L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hudl, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Höglin, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Dung, N. H.
    Gómez, Cesar Pay
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Bruck, E.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Magnetocrystalline anisotropy and the magnetocaloric effect in Fe2P2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, no 9, p. 094440-Article in journal (Refereed)
    Abstract [en]

    Magnetic and magnetocaloric properties of high-purity, giant magnetocaloric polycrystalline and single-crystalline Fe2P are investigated. Fe2P displays a moderate magnetic entropy change, which spans over 70 K and the presence of strong magnetization anisotropy proves this system is not fully itinerant but displays a mix of itinerant and localized magnetism. The properties of pure Fe2P are compared to those of giant magnetocaloric (Fe,Mn)2(P,A) (where A = As, Ge, Si) compounds helping understand the exceptional characteristics shown by the latter, which are so promising for heat pump and energy conversion applications.

  • 4.
    Casillas-Trujillo, Luis
    et al.
    Linköping Univ, Dept Phys Chem & Biol IFM, S-58183 Linköping, Sweden..
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Ek, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nygård, Magnus M.
    Inst Energy Technol, Dept Neutron Mat Characterizat, NO-2027 Kjeller, Norway..
    Sorby, Magnus H.
    Inst Energy Technol, Dept Neutron Mat Characterizat, NO-2027 Kjeller, Norway..
    Hauback, Bjorn C.
    Inst Energy Technol, Dept Neutron Mat Characterizat, NO-2027 Kjeller, Norway..
    Abrikosov, Igor A.
    Linköping Univ, Dept Phys Chem & Biol IFM, S-58183 Linköping, Sweden.;Natl Univ Sci & Technol MISIS, Mat Modeling & Dev Lab, Moscow 119049, Russia..
    Alling, Björn
    Linköping Univ, Dept Phys Chem & Biol IFM, S-58183 Linköping, Sweden..
    Interstitial carbon in bcc HfNbTiVZr high-entropy alloy from first principles2020In: Physical Review Materials, E-ISSN 2475-9953, Vol. 4, no 12, article id 123601Article in journal (Refereed)
    Abstract [en]

    The remarkable mechanical properties of high-entropy alloys can be further improved by interstitial alloying. In this work we employ density functional theory calculations to study the solution energies of dilute carbon interstitial atoms in tetrahedral and octahedral sites in bcc HfNbTiVZr. Our results indicate that carbon interstitials in tetrahedral sites are unstable, and the preferred octahedral sites present a large spread in the energy of solution. The inclusion of carbon interstitials induces large structural relaxations with long-range effects. The effect of local chemical environment on the energy of solution is investigated by performing a local cluster expansion including studies of its correlation with the carbon atomic Voronoi volume. However, the spread in solution energetics cannot be explained with a local environment analysis only pointing towards a complex, long-range influence of interstitial carbon in this alloy.

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  • 5.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden.
    Delczeg-Czirjak, Erna Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Iusan, Diana
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Pereiro, Manuel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Roy, P.
    Radboud Univ Nijmegen, Inst Mol & Mat, Heyendaalseweg 135, NL-6525 AJ Nijmegen, Netherlands.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Lohstroh, W.
    Tech Univ Munich, Heinz Maier Leibnitz Zentrum MLZ, Garching Bei Munchen, Lichtenbergstr, D-185748 Garching, Germany.
    Mutka, H.
    Inst Laue Langevin, BP 156, F-38042 Grenoble 9, France.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Deen, P. P.
    European Spallat Source ESS ERIC, Box 176, SE-22100 Lund, Sweden;Univ Copenhagen, Nanosci Ctr, Niels Bohr Inst, DK-2100 Copenhagen O, Denmark.
    Magnetocaloric effect in Fe2P: Magnetic and phonon degrees of freedom2019In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 17, article id 174437Article in journal (Refereed)
    Abstract [en]

    Devices based on magnetocaloric materials provide great hope for environmentally friendly and energy efficient cooling that does not rely on the use of harmful gasses. Fe2P based compounds are alloys that have shown great potential for magnetocaloric devices. The magnetic behavior in Fe2P is characterized by a strong magnetocaloric effect that coexists with a first-order magnetic transition (FOMT). Neutron diffraction and inelastic scattering, Mossbauer spectroscopy, and first-principles calculations have been used to determine the structural and magnetic state of Fe2P around the FOMT. The results reveal that ferromagnetic moments in the ordered phase are perturbed at the FOMT such that the moments cant away from the principle direction within a small temperature region. The acoustic-phonon modes reveal a temperature-dependent nonzero energy gap in the magnetically ordered phase that falls to zero at the FOMT. The interplay between the FOMT and the phonon energy gap indicates hybridization between magnetic modes strongly affected by spin-orbit coupling and phonon modes leading to magnon-phonon quasiparticles that drive the magnetocaloric effect.

  • 6.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Mikael
    Iusan, Diana
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Delczeg-Czirjak, Erna Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetic and mechanical effects of Mn substitutions in AlFe2B22019In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 482, p. 54-60Article in journal (Refereed)
    Abstract [en]

    The mechanical and magnetic properties of the newly discovered MAB-phase class of materials based upon AlFe2B2 were investigated. The samples were synthesised from stoichiometric amounts of all constituent elements. X-ray diffraction shows that the main phase is orthorhombic with an elongated b-axis, similar to AlFe2B2. The low hardness and visual inspection of the samples after deformation indicate that these compounds are deformed via a delamination process. When substituting iron in AlFe2B2 with manganese, the magnetism in the system goes from being ferro- to antiferromagnetic via a disordered ferrimagnetic phase exhibited by AlFeMnB2. Density functional theory calculations indicate a weakening of the magnetic interactions among the transitions metal ions as iron is substituted by manganese in AlFe2B2. The Mn-Mn exchange interactions in AlMn2B2 are found to be very small.

  • 7.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Mikael Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sarkar, Tapati
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Delczeg-Czirjak, Erna K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Bergqvist, Lars
    Hansen, Thomas C.
    Beran, Premysl
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetic structure of the magnetocaloric compound AlFe2B22016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 654, p. 784-791Article in journal (Refereed)
    Abstract [en]

    The crystal and magnetic structures of AlFe2B2 have been studied with a combination of X-ray and neutron diffraction and electronic structure calculations. The magnetic and magnetocaloric properties have been investigated by magnetisation measurements. The samples have been produced using high temperature synthesis and subsequent heat treatments. The compound crystallises in the orthorhombic crystal system Cmmm and it orders ferromagnetically at 285 K through a second order phase transition. At temperatures below the magnetic transition the magnetic moments align along the crystallographic a-axis. The magnetic entropy change from 0 to 800 kA/m was found to be - 1.3 J/K kg at the magnetic transition temperature.

  • 8.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Beran, Premysl
    ASCR, Inst Nucl Phys, Hlavni 130, Rez 25068, Czech Republic.
    Vennström, Marie
    AB Sandvik Mat Technol, SE-81181 Sandviken, Sweden.
    Danielsson, Therese
    Etteplan Sweden AB, SE-17154 Solna, Sweden.
    Ronneteg, Sabina
    AB Sandvik Mat Technol, SE-81181 Sandviken, Sweden.
    Höglin, Viktor
    Scienta Sauna Syst AB, SE-75228 Uppsala, Sweden.
    Lindell, David
    Swerea KIMAB AB, Box 7047, SE-16407 Kista, Sweden.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    André, Gilles
    CEA Saclay, LLB, F-91191 Gif Sur Yvette, France.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Low temperature magneto-structural transitions in Mn3Ni20P62016In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 237, p. 343-348Article in journal (Refereed)
    Abstract [en]

    Abstract X-ray and neutron powder diffraction has been used to determine the crystal and magnetic structure of Mn3Ni20P6. The crystal structure can be described as cubic with space group Fm 3 ¯ m (225) without any nuclear phase transformation within studied temperature interval from room temperature down to 4 K. The magnetic structure of Mn3Ni20P6 is complex with two independent magnetic positions for the Mn atoms and the compound passes three successive magnetic phase transitions during cooling. At 30 K the spins of the Mn atoms on the Wyckoff 4a site (Mn1) order to form a primitive cubic antiferromagnetic structure with propagation vector k=(0 0 1). Between 29 and 26 K the Mn atoms on the Wyckoff 8c site (Mn2) order independently on already ordered Mn1 magnetic structure forming a commensurate antiferromagnetic structure with propagation vector k=(0 0 ½) and below 26 K, both Mn positions order to form an incommensurate helical structure with propagation vector k=(0 0 ~0.45). Magnetization vs. temperature curve of Mn3Ni20P6 shows a steep increase indicating some magnetic ordering below 230 K and a sharp field dependent anomaly in a narrow temperature range around 30 K.

  • 9.
    Cedervall, Johan
    et al.
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.;Rutherford Appleton Lab, ISIS Pulsed Neutron & Muon Facil, Harwell Campus, Didcot OX11 0QX, Oxon, England..
    Clulow, Rebecca
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Boström, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Max Planck Inst Solid State Res, Heisenbergsstr 1, D-70569 Stuttgart, Germany..
    Joshi, Deep C.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Andersson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics. Chalmers Univ Technol, Dept Chem & Chem Engn, S-41296 Gothenburg, Sweden..
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Beran, Premysl
    Acad Sci Czech Republ, Nucl Phys Inst, Rez 25068, Czech Republic.;European Spallat Source ESS ERIC, Box 176, S-22100 Lund, Sweden..
    Smith, Ronald, I
    Rutherford Appleton Lab, ISIS Pulsed Neutron & Muon Facil, Harwell Campus, Didcot OX11 0QX, Oxon, England..
    Tseng, Jo-Chi
    Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22607 Hamburg, Germany..
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Berastegui, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Shafeie, Samrand
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Chalmers Univ Technol, Dept Phys, S-41296 Gothenburg, Sweden..
    Phase stability and structural transitions in compositionally complex LnMO(3) perovskites2021In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 300, article id 122213Article in journal (Refereed)
    Abstract [en]

    Entropy stabilised materials have possibilities for tailoring functionalities to overcome challenges in materials science. The concept of configurational entropy can also be applied to metal oxides, but it is unclear whether these could be considered as solid solutions in the case of perovskite-structured oxides and if the configurational entropy plays a stabilising role. In this study, compositionally complex perovskite oxides, LnMO(3) (Ln = La, Nd, Sm, Ca and Sr, M = Ti, Cr, Mn, Fe, Co, Ni, and Cu), are investigated for their phase stability and magnetic behaviour. Phase-pure samples were synthesised, and the room temperature structures were found to crystallise in either Pnma or R (3) over barc space groups, depending on the composition and the resulting tolerance factor, while the structural transition temperatures correlate with the pseudo cubic unit cell volume. The techniques used included diffraction with X-rays and neutrons, both ex- and in-situ, X-ray photoelectron spectroscopy, magnetometry as well as electron microscopy. Neutron diffraction studies on one sample reveal that no oxygen vacancies are found in the structure and that the magnetic properties are ferrimagnetic-like with magnetic moments mainly coupled antiferromagnetically along the crystallographic c-direction. X-ray photoelectron spectroscopy gave indications of the oxidation states of the constituting ions where several mixed oxidation states are observed in these valence-compensated perovskites.

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  • 10.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Mössbauer study of the magnetocaloric compound AlFe2B22016In: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 237, article id 47Article in journal (Refereed)
    Abstract [en]

    Mössbauer spectroscopy in the ferromagnetic AlFe2B2 reveals Tc=299 K and shows good agreement with magnetic measurements. The crystals are plate-shaped. The flakes are found from X-ray diffraction to be in the crystallographic ac-plane in the orthorhombic system. The axes of the principle electric field gradient tensor are, by symmetry, colinear with the crystal a-, b- and c-axes. By using information about the quadrupole splitting and line asymmetry in the paramagnetic regime together with the quadrupole shift of the resonance lines in the ferromagnetic regime the magnetic hyperfine field direction is found to be in the ab-plane having an angle =40° to the b-axis.

  • 11.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Ivanov, Sergey A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Karpov Inst Phys Chem, Ctr Mat Sci, Vorontsovo Pole 10, Moscow 105064, Russia;Uppsala Univ, Dept Engn Sci, Box 534, S-75121 Uppsala, Sweden.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala Univ, Dept Chem, Angstrom Lab, Box 538, S-75121 Uppsala, Sweden.
    Beran, Premysl
    ESS, Tunavagen 24, S-22363 Lund, Sweden;Acad Sci Czech Republ, Nucl Phys Inst, Rez 25068, Czech Republic.
    Andersson, Mikael S.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Faske, Tom
    Tech Univ Darmstadt, Inst Mat & Geowissensch, Alarich Weiss Str 2, D-64287 Darmstadt, Germany.
    Bazuev, Gennadii V.
    Russian Acad Sci, Inst Solid State Chem, Ural Branch, Ekaterinburg 620990, Russia.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    On the structural and magnetic properties of the double perovskite Nd2NiMnO62019In: Journal of materials science. Materials in electronics, ISSN 0957-4522, E-ISSN 1573-482X, Vol. 30, no 17, p. 16571-16578Article in journal (Refereed)
    Abstract [en]

    The structural, electronic and magnetic properties of phase pure and stoichiometric samples of the double perovskite Nd2NiMnO6. Photoectron spectroscopy revels a mixed valence of the transition metal sites where Ni has 3+/2+ oxidation states and Mn has 3+/4+. The compound orders ferromagnetically at 195 K. The magnetic structure was determined from the refinement of the neutron diffraction data. The results suggests that the B-site magnetic moments align along the crystallographic a-direction.

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  • 12.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Kontos, Sofia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hansen, Thomas C.
    Balmes, Olivier
    Martinez-Casado, Francisco Javier
    Matej, Zdenek
    Beran, Premysl
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetostructural transition in Fe5SiB2 observed with neutron diffraction2016In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 235, p. 113-118Article in journal (Refereed)
    Abstract [en]

    The crystal and magnetic structure of Fe5SiB2 has been studied by a combination of X-ray and neutron diffraction. Also, the magnetocrystalline anisotropy energy constant has been estimated from magnetisation measurements. High quality samples have been prepared using high temperature synthesis and subsequent heat treatment protocols. The crystal structure is tetragonal within the space group I4/mcm and the compound behaves ferromagnetically with a Curie temperature of 760 K. At 172 K a spin reorientation occurs in the compound and the magnetic moments go from aligning along the c-axis (high T) down to the ab-plane (low T). The magnetocrystalline anisotropy energy constant has been estimated to 03 MJ/m(3) at 300 K.

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  • 13.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nonnet, Elise
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Hedlund, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Werwinski, Miroslaw
    Institute of Molecular Physics, Polish Academy of Sciences.
    Edström, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Department of Materials Theory, ETH Zürich.
    Rusz, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of cobalt substitution on the magnetic properties of Fe5PB22018In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 57, no 2, p. 777-784Article in journal (Refereed)
    Abstract [en]

    In this study the effects of cobalt substitutions in Fe5PB2 have been studied. An increased cobalt content reduces the magnetic exchange interactions. This has been concluded from a large, linear decrease in both the Curie temperature as well as the saturated magnetic moment. At high cobalt concentrations, cobalt prefers to order at the M(2) position in the crystal structure. A tunable Curie transition like this shows some prerequisites for magnetic cooling applications.

    The substitutional effects of cobalt in (Fe1–xCox)5PB2 have been studied with respect to crystalline structure and chemical order with X-ray diffraction and Mössbauer spectroscopy. The magnetic properties have been determined from magnetic measurements, and density functional theory calculations have been performed for the magnetic properties of both the end compounds, as well as the chemically disordered intermediate compounds. The crystal structure of (Fe1–xCox)5PB2 is tetragonal (space group I4/mcm) with two different metal sites, with a preference for cobalt atoms in the M(2) position (4c) at higher cobalt contents. The substitution also affects the magnetic properties with a decrease of the Curie temperature (TC) with increasing cobalt content, from 622 to 152 K for Fe5PB2 and (Fe0.3Co0.7)5PB2, respectively. Thus, the Curie temperature is dependent on composition, and it is possible to tune TC to a temperature near room temperature, which is one prerequisite for magnetic cooling materials.

  • 14.
    Chou, Chia-Ying
    et al.
    KTH Royal Inst Technol, Dept Mat Sci & Engn, Brinellvagen 23, S-10044 Stockholm, Sweden.
    Karlsson, Dennis
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Pettersson, Niklas Hollander
    KTH Royal Inst Technol, Dept Mat Sci & Engn, Brinellvagen 23, S-10044 Stockholm, Sweden.
    Helander, Thomas
    Kanthal AB, Box 502, S-73427 Hallstahammar, Sweden.
    Harlin, Peter
    Sandv Addit Mfg, S-81181 Sandviken, Sweden.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Odqvist, Joakim
    KTH Royal Inst Technol, Dept Mat Sci & Engn, Brinellvagen 23, S-10044 Stockholm, Sweden.
    Lindwall, Greta
    KTH Royal Inst Technol, Dept Mat Sci & Engn, Brinellvagen 23, S-10044 Stockholm, Sweden.
    Precipitation Kinetics During Post-heat Treatment of an Additively Manufactured Ferritic Stainless Steel2022In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 53, no 8, p. 3073-3082Article in journal (Refereed)
    Abstract [en]

    The microstructure response of laser-powder bed fusion (L-PBF)-processed ferritic stainless steel (AISI 441) during post-heat treatments is studied in detail. Focus is on the precipitation kinetics of the Nb-rich phases: Laves (Fe2Nb) and the cubic carbo-nitride (NbC), as well as the grain structure evolution. The evolution of the precipitates is characterized using scanning and transmission electron microscopy (SEM and TEM) and the experimental results are used to calibrate precipitation kinetics simulations using the precipitation module (TC-PRISMA) within the Thermo-Calc Software package. The calculations reproduce the main trend for both the mean radii for the Laves phase and the NbC, and the amount of Laves phase, as a function of temperature. The calibrated model can be used to optimize the post-heat treatment of additively manufactured ferritic stainless steel components and offer a creator tool for process and structure linkages in an integrated computational materials engineering (ICME) framework for alloy and process development of additively manufactured ferritic steels.

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  • 15.
    Clulow, Rebecca
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hedlund, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Vishina, Alena
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetic and Structural Properties of the Fe5Si1-xGexB2 System2022In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 316, article id 123576Article in journal (Refereed)
    Abstract [en]

    A series of compounds with compositions Fe5Si1-xGexB2 were synthesised and their structural and magnetic properties were investigated. The Mo5SiB2-type structure with tetragonal I4/mcm space group is maintained for all compounds with x < 0.15, which is estimated as the compositional limit of the system. The unit cell pa-rameters expand with Ge content before reaching a plateau of a = 5.5581(1) and c = 10.3545(1) angstrom at x = 0.15. The saturation magnetisation (MS) decreased slightly with increasing Ge content whilst the magnetocrystalline anisotropy energy (MAE) remains almost unaffected. The Curie temperature for all compounds studied is at 790 K whilst the spin-reorientation temperature shows suppression from 172 K to 101 K where x = 0.15. Ab Initio calculations reveal an increase in MAE for compositions up to x = 0.25 and a decreased magnitude of MAE of-0.14 MJ/m3 for the hypothetical compound Fe5GeB2 relative to the parent compound Fe5SiB2.

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  • 16.
    Clulow, Rebecca
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Pramanik, Prativa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Stolpe, Amanda
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström. Mid Sweden Univ, FSCN Res Ctr Surface & Colloid Engn, S-85170 Sundsvall, Sweden..
    Joshi, Deep C.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Henry, Paul F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Rutherford Appleton Lab, ISIS Pulsed Neutron & Muon Facil, Didcot OX11 0QX, England..
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Phase Stability and Magnetic Properties of Compositionally Complex n=2 Ruddlesden-Popper Perovskites2024In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 63, no 15, p. 6616-6625Article in journal (Refereed)
    Abstract [en]

    Four new compositionally complex perovskites with multiple (four or more) cations on the B site of the perovskites have been studied. The materials have the general formula La0.5Sr2.5(M)2O7−δ (M = Ti, Mn, Fe, Co, and Ni) and have been synthesized via conventional solid-state synthesis. The compounds are the first reported examples of compositionally complex n = 2 Ruddlesden–Popper perovskites. The structure and properties of the materials have been determined using powder X-ray diffraction, neutron diffraction, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and magnetometry. The materials are isostructural and adopt the archetypal I4/mmm space group with the following unit cell parameters: a ∼ 3.84 Å, and c ∼ 20.1 Å. The measured compositions from energy dispersive X-ray spectroscopy were La0.51(2)Sr2.57(7)Ti0.41(2)Mn0.41(2)Fe0.39(2)Co0.38(1)Ni0.34(1)O7−δ, La0.59(4)Sr2.29(23)Mn0.58(5)Fe0.56(6)Co0.55(6)Ni0.42(4)O7−δ, La0.54(2)Sr2.49(13)Mn0.41(2)Fe0.81(5)Co0.39(3)Ni0.36(3)O7−δ, and La0.53(4)Sr2.55(19)Mn0.67(6)Fe0.64(5)Co0.31(2)Ni0.30(3)O7−δ. No magnetic contribution is observed in the neutron diffraction data, and magnetometry indicates a spin glass transition at low temperatures.

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  • 17.
    Dahlqvist, M.
    et al.
    Linkoping Univ, Dept Phys Chem & Biol, Thin Film Phys, SE-58183 Linkoping, Sweden..
    Ingason, A. S.
    Linkoping Univ, Dept Phys Chem & Biol, Thin Film Phys, SE-58183 Linkoping, Sweden..
    Alling, B.
    Linkoping Univ, Dept Phys Chem & Biol, Thin Film Phys, SE-58183 Linkoping, Sweden..
    Magnus, Fridrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Thore, A.
    Linkoping Univ, Dept Phys Chem & Biol, Thin Film Phys, SE-58183 Linkoping, Sweden..
    Petruhins, A.
    Linkoping Univ, Dept Phys Chem & Biol, Thin Film Phys, SE-58183 Linkoping, Sweden..
    Mockute, A.
    Linkoping Univ, Dept Phys Chem & Biol, Thin Film Phys, SE-58183 Linkoping, Sweden..
    Arnalds, U. B.
    Univ Iceland, Inst Sci, IS-107 Reykjavik, Iceland..
    Sahlberg, Martin Häggblad
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Abrikosov, I. A.
    Linkoping Univ, Dept Phys Chem & Biol, Theoret Phys, SE-58183 Linkoping, Sweden.;Natl Univ Sci & Technol MISIS, Mat Modeling & Dev Lab, Moscow 119049, Russia.;Tomsk State Univ, LOCOMAS Lab, Tomsk 634050, Russia..
    Rosen, J.
    Linkoping Univ, Dept Phys Chem & Biol, Thin Film Phys, SE-58183 Linkoping, Sweden..
    Magnetically driven anisotropic structural changes in the atomic laminate Mn2GaC2016In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 93, no 1, article id 014410Article in journal (Refereed)
    Abstract [en]

    Inherently layered magnetic materials, such as magnetic M(n+1)AX(n) (MAX) phases, offer an intriguing perspective for use in spintronics applications and as ideal model systems for fundamental studies of complex magnetic phenomena. The MAX phase composition M(n+1)AX(n) consists of M(n+1)AX(n) blocks separated by atomically thin A-layers where M is a transition metal, A an A-group element, X refers to carbon and/or nitrogen, and n is typically 1, 2, or 3. Here, we show that the recently discovered magnetic Mn2GaC MAX phase displays structural changes linked to the magnetic anisotropy, and a rich magnetic phase diagram which can be manipulated through temperature and magnetic field. Using first-principles calculations and Monte Carlo simulations, an essentially one-dimensional (1D) interlayer plethora of two-dimensioanl (2D) Mn-C-Mn trilayers with robust intralayer ferromagnetic spin coupling was revealed. The complex transitions between them were observed to induce magnetically driven anisotropic structural changes. The magnetic behavior as well as structural changes dependent on the temperature and applied magnetic field are explained by the large number of low energy, i.e., close to degenerate, collinear and noncollinear spin configurations that become accessible to the system with a change in volume. These results indicate that the magnetic state can be directly controlled by an applied pressure or through the introduction of stress and show promise for the use of Mn2GaC MAX phases in future magnetoelectric and magnetocaloric applications.

  • 18.
    Dobrovetska, Oksana
    et al.
    Lviv Polytech Natl Univ, Inst Chem, Bandery 12, UA-79013 Lvov, Ukraine.
    Saldan, Ivan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström. Ivan Franko Natl Univ Lviv, Fac Chem, Kyryla & Mefodia 6, UA-79005 Lvov, Ukraine.
    Orovcik, Lubomir
    Slovak Acad Sci, Inst Mat & Machine Mech, Dubrvska Cesta 9, Bratislava 84513, Slovakia.
    Karlsson, Dennis
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Häggblad Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Semenyuk, Yuriy
    Ivan Franko Natl Univ Lviv, Fac Chem, Kyryla & Mefodia 6, UA-79005 Lvov, Ukraine.
    Pereviznyk, Orest
    Ivan Franko Natl Univ Lviv, Fac Chem, Kyryla & Mefodia 6, UA-79005 Lvov, Ukraine.
    Reshetnyak, Oleksandr
    Ivan Franko Natl Univ Lviv, Fac Chem, Kyryla & Mefodia 6, UA-79005 Lvov, Ukraine.
    Kuntyi, Orest
    Lviv Polytech Natl Univ, Inst Chem, Bandery 12, UA-79013 Lvov, Ukraine.
    Mertsalo, Ivanna
    Lviv Polytech Natl Univ, Inst Chem, Bandery 12, UA-79013 Lvov, Ukraine.
    Serkiz, Roman
    Ivan Franko Natl Univ Lviv, Ctr Low Temp Studies, Dragomanova 50, UA-79005 Lvov, Ukraine.
    Stelmakhovych, Bohdan
    Ivan Franko Natl Univ Lviv, Fac Chem, Kyryla & Mefodia 6, UA-79005 Lvov, Ukraine.
    Electrocatalytic activity of Pd-Au nanoalloys during methanol oxidation reaction2020In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 45, no 7, p. 4444-4456Article in journal (Refereed)
    Abstract [en]

    Methanol fuel cells are very promising power source due to its high efficiency and low emissions of pollutants but their commercialization is hindered by development of the effective catalysts. Bimetallic nanostructured catalysts have been used to increase the effectiveness of methanol electrooxidation. Their high electrocatalytic activity can be accounted largely by the difference in electronegativity of two metals (e.g. Pd and Au), that resulting in gradual Auδ+→Auδ– transition with the increase in Pd content. Therefore, gold-enriched bimetallic Pd-Aunano were recommended as catalysts for oxidation processes since they are characterized by the presence of Auδ+ on their surface. Deposition of Pd, Au and Pd–Au nanoparticles (~50–350 nm) were carried out in dimethyl sulfoxide by pulsed mode of electrolysis directly on electrode surface. Cyclic voltammetry was the main method to study catalytic properties of the modified electrode in the anode oxidation process of methanol. It was found that oxidation rate on the electrode surface modified by bimetallic Pd–Au nanoparticles is ~1.5 times higher as compared to that in the case of electrodes modified by Pd or Au monometallic nanoparticles individually. In order to find highly active, selective, and stable catalysts for methanol electrocatalytic oxidation reaction additional studies are needed to understand the role of electrode surface charge and local OH ions concentration from alkali solution.

  • 19.
    Ek, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Fjellvåg, Øystein S.
    Institute for Energy Technology, Department of Neutron Materials Characterization, P.O Box 40, NO-2027, Kjeller, Norway.
    Vajeeston, Ponniah
    Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo, P.O Box 1033, NO-0315, Oslo, Norway.
    Armstrong, Jeff
    ISIS Pulsed Neutron and Muon source, Rutherford Appleton Laboratory, OX11 0QX, Didcot, United Kingdom.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Häussermann, Ulrich
    Department of Materials and Environmental Chemistry, Stockholm University, SE-10691, Stockholm, Sweden.
    Vibrational properties of High Entropy Alloy based metal hydrides probed by inelastic neutron scattering2021In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 877, article id 160320Article in journal (Refereed)
    Abstract [en]

    The vibrational properties of several High Entropy Alloy (HEA) based metal hydrides are investigated by inelastic neutron scattering (INS). HEAs have recently emerged as a new type of materials with a wide range of intriguing properties and potential applications such as hydrogen storage. The special properties of HEAs are believed to originate from the disordered lattice and internal strain that is introduced from the differences in atomic radii. This makes HEA hydrides provide an intriguing situation for the local H coordination, of several different transition metals. INS spectra were collected on a series of HEA-based metal hydrides starting with TiVNbHx and subsequently adding Zr and Hf to increase the atomic size mismatch. A general feature of the spectra are the optical peaks centered around an energy loss of 150 meV that can be attributed to hydrogen vibrations in a tetrahedral environment. Upon the addition of Zr and Hf, a shoulder appears on the optical peak at lower energy transfers that after comparison with in silico calculated INS spectra is indicative of hydrogen also occupying octahedral sites in the structure.

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  • 20.
    Ek, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nedumkandathil, Reji
    Stockholm Univ, Dept Mat & Environm Chem, Stockholm, Sweden.
    Johansson, Robert
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Montero, Jorge
    Univ Paris Est, Inst Chim & Mat Paris Est, CNRS, Champs Sur Marne, France.
    Zlotea, Claudia
    Univ Paris Est, Inst Chim & Mat Paris Est, CNRS, Champs Sur Marne, France.
    Andersson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Chalmers Univ Technol, Dept Chem & Chem Engn, Gothenburg, Sweden.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Tang, Chiu
    Diamond Light Source, Harwell Sci & Innovat Campus, Didcot, Oxon, England.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Haussermann, Ulrich
    Stockholm Univ, Dept Mat & Environm Chem, Stockholm, Sweden.
    Hydrogen induced structure and property changes in Eu3Si42019In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 277, p. 37-45Article in journal (Refereed)
    Abstract [en]

    Hydrides Eu3Si4H2-X were obtained by exposing the Zintl phase Eu3Si4 to a hydrogen atmosphere at a pressure of 30 bar and temperatures from 25 to 300 degrees C. Structural analysis using powder X-ray diffraction (PXRD) data suggested that hydrogenations in a temperature range 25-200 degrees C afford a uniform hydride phase with an orthorhombic structure (Immm, a approximate to 4.40 angstrom, b approximate to 3.97 angstrom, c approximate to 19.8 angstrom), whereas at 300 degrees C mixtures of two orthorhombic phases with c approximate to 19.86 and approximate to 19.58 angstrom were obtained. The assignment of a composition Eu3Si4H2+x is based on first principles DFT calculations, which indicated a distinct crystallographic site for H in the Eu3Si4 structure. In this position, H atoms are coordinated in a tetrahedral fashion by Eu atoms. The resulting hydride Eu3Si4H2 is stable by -0.46 eV/H atom with respect to Eu3Si4 and gaseous H-2. Deviations between the lattice parameters of the DFT optimized Eu3Si4H2 structure and the ones extracted from PXRD patterns pointed to the presence of additional H in interstitials also involving Si atoms. Subsequent DFT modeling of compositions Eu3Si4H3 and Eu3Si4H4 showed considerably better agreement to the experimental unit cell volumes. It was then concluded that the hydrides of Eu3Si4 have a composition Eu3Si4H2+x (x < 2) and are disordered with respect to H in Si2Eu3 interstitials. Eu3Si4 is a ferromagnet with a Tc at about 120 K. Ferromagnetism is effectively quenched in Eu3Si4H2+x. The effective magnetic moment for both materials is 7.5 pg which is typical for compounds containing Eu2+ 4f(7) ions.

  • 21.
    Ek, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nygård, Magnus M.
    Institute for Energy Technology, Department for Neutron Materials Characterization, P.O. Box 40, Kjeller NO-2027 Norway.
    Pavan, Adriano F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Montero, Jorge
    Université de Paris Est, Institut de Chimie et des Matériaux Paris Est, CNRS, UPEC, 94320 Thiais, France.
    Henry, Paul F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Rutherford Appleton Laboratory.
    Sørby, Magnus H.
    Institute for Energy Technology, Department for Neutron Materials Characterization, P.O. Box 40, Kjeller NO-2027 Norway.
    Witman, Matthew
    Sandia National Laboratories, Livermore, California 94551, United States.
    Stavila, Vitalie
    Sandia National Laboratories, Livermore, California 94551, United States.
    Zlotea, Claudia
    Université de Paris Est, Institut de Chimie et des Matériaux Paris Est, CNRS, UPEC, 94320 Thiais, France.
    Hauback, Bjørn C.
    Institute for Energy Technology, Department for Neutron Materials Characterization, P.O. Box 40, Kjeller NO-2027 Norway.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Elucidating the Effects of the Composition on Hydrogen Sorption in TiVZrNbHf-Based High-Entropy Alloys2021In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 60, no 2, p. 1124-1132Article in journal (Refereed)
    Abstract [en]

    A number of high-entropy alloys (HEAs) in the TiVZrNbHf system have been synthesized by arc melting and systematically evaluated for their hydrogen sorption characteristics. A total of 21 alloys with varying elemental compositions were investigated, and 17 of them form body-centered-cubic (bcc) solid solutions in the as-cast state. A total of 15 alloys form either face-centered-cubic (fcc) or body-centered-tetragonal (bct) hydrides after exposure to gaseous hydrogen with hydrogen per metal ratios (H/M) as high as 2.0. Linear trends are observed between the volumetric expansion per metal atom [(V/Z)fcc/bct – (V/Z)bcc/hcp]/(V/Z)bcc/hcp with the valence electron concentration and average Pauling electronegativity (χp) of the alloys. However, no correlation was observed between the atomic size mismatch, δ, and any investigated hydrogen sorption property such as the maximum storage capacity or onset temperature for hydrogen release.

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  • 22.
    Ericsson, A.
    et al.
    Lund Univ, Div Solid Mech, POB 118, SE-75120 Lund, Sweden..
    Pacheco, Victor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lindwall, J.
    Luleå Tech Univ, Mech Solid Mat, SE-97187 Luleå, Sweden..
    Hallberg, H.
    Lund Univ, Div Solid Mech, POB 118, SE-75120 Lund, Sweden..
    Fisk, M.
    Lund Univ, Div Solid Mech, POB 118, SE-75120 Lund, Sweden.;Malmö Univ, Mat Sci & Appl Math, SE-20506 Malmö, Sweden..
    Transient nucleation in selective laser melting of Zr-based bulk metallic glass2020In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 195, article id 108958Article in journal (Refereed)
    Abstract [en]

    The crystallization rate during selective laser melting (SLM) of bulk metallic glasses (BMG) is a critical factor in maintaining the material's amorphous structure. To increase the understanding of the interplay between the SLM process and the crystallization behavior of BMGs, a numerical model based on the classical nucleation theory has been developed that accounts for the rapid temperature changes associated with SLM. The model is applied to SLM of a Zr-based BMG and it is shown that the transient effects, accounted for by the model, reduce the nucleation rate by up to 15 orders of magnitude below the steady-state nucleation rate on cooling, resulting in less nuclei during the build process. The capability of the proposed modelling approach is demonstrated by comparing the resulting crystalline volume fraction to experimental findings. The agreement between model predictions and the experimental results clearly suggests that transient nucleation effects must be accounted for when considering the crystallization rate during SLM processing of BMGs.

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  • 23.
    Ericsson, Anders
    et al.
    Lund University.
    Pacheco, Victor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Marattukalam, Jithin J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Dalgliesh, Robert M.
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Fisk, Martin
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Crystallization of a Zr-based metallic glass produced by laser powder bed fusion and suction casting2021In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 571, article id 120891Article in journal (Refereed)
    Abstract [en]

    The crystallization behavior during low-temperature annealing of samples of the Zr59.3Cu28.8Al10.4Nb1.5 (at%) bulk metallic glass produced by suction casting and the laser powder bed fusion (LPBF) process was studied with small-angle neutron scattering (SANS), X-ray diffraction, and scanning electron microscopy. The in-situ SANS measurements during isothermal annealing reveal that the phase separation in the LPBF processed material proceeds at a smaller characteristic length-scale than the cast material. Quantitative analysis of the SANS data shows that, while the crystallization process in both materials proceeds through rapid nucleation followed by diffusion-limited growth, the LPBF processed material crystallizes with a smaller cluster size and at a higher rate. The smaller cluster size is attributed to the elevated oxygen content in the LPBF processed material which reduces the nucleation barrier and thus the thermal stability.

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  • 24.
    Eriksson, Rickard
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Sobkowiak, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ångström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Formation of Tavorite-Type LiFeSO4F Followed by In Situ X-ray Diffraction2015In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 298, p. 363-368Article in journal (Refereed)
    Abstract [en]

    The tavorite-type polymorph of LiFeSO4F has recently attracted substantial attention as a positive elec- trode material for lithium ion batteries. The synthesis of this material is generally considered to rely on a topotactic exchange of water (H2O) for lithium (Li) and fluorine (F) within the structurally similar hy- drated iron sulfate precursor (FeSO4·H2O) when reacted with lithium fluoride (LiF). However, there have also been discussions in the literature regarding the possibility of a non-topotactic reaction mechanism between lithium sulfate (Li2SO4) and iron fluoride (FeF2) in tetraethylene glycol (TEG) as reaction medium. In this work, we use in situ X-ray diffraction to continuously follow the formation of LiFeSO4F from the two suggested precursor mixtures in a setup aimed to mimic the conditions of a solvothermal autoclave synthesis. It is demonstrated that LiFeSO4F is formed directly from FeSO4·H2O and LiF, in agreement with the proposed topotactic mechanism. The Li2SO4 and FeF2 precursors, on the other hand, are shown to rapidly transform into FeSO4·H2O and LiF with the water originating from the highly hygroscopic TEG before a subsequent formation of LiFeSO4F is initiated. The results highlight the importance of the FeSO4·H2O precursor in obtaining the tavorite-type LiFeSO4F, as it is observed in both reaction routes.

  • 25.
    Fang, Hailiang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Casado, Francisco Javier Martinez
    Lund Univ, MAX IV Lab, Box 118, S-22100 Lund, Sweden..
    Matej, Zdenek
    Lund Univ, MAX IV Lab, Box 118, S-22100 Lund, Sweden..
    Bednarcik, Jozef
    Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22603 Hamburg, Germany..
    Ångstrom, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Berastegui, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Insights into formation and stability of tau-MnAlZ(x) (Z = C and B)2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 692, p. 198-203Article in journal (Refereed)
    Abstract [en]

    The tau-phase MnAl alloys are promising candidate for rare earth free permanent magnets. In this study, In order to better understand the MnAl epsilon ->tau phase transition mechanism in a continuous cooling process and metastable MnAl tau-phase high temperature stability, Mn0.54Al0.46, Mn0.55Al0.45C0.02 and Mn0.55Al0.45B0.02 alloys were systematically studied by in situ synchrotron X-ray powder diffraction (SR-XRD). The relationship between tau-phase formation tendency and different cooling rates of Mn0.55Al0.45C0.02 was investigated. Besides, the high temperature stabilities of undoped tau-MnAl and carbon/boron doped tau-MnAl were studied. Differential thermal analysis (DTA) was also employed to study the phase transformation as well. The research results show that a high cooling rate of 600 degrees C/min leads to a 50/50 wt% mixture of epsilon- and tau-phase; almost pure tau-phase was obtained when cooled at a moderate cooling rate of 10 degrees C/min; while for a slow cooling rate of 2 degrees C/min, the tau-phase partially decomposed into beta and gamma(2) phases. No intermediate epsilon'-phase was observed during the epsilon ->tau phase transition during the experiments. For the boron and carbon doped tau-MnAl, the 800 degrees C high temperature stability experiments reveal that C stabilizes the tau-MnAl while doped B destabilises the tetragonal structure and it decomposes into beta- and gamma(2)-phases.

  • 26.
    Fang, Hailiang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hedlund, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Shafeie, Samrand
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Deledda, Stefano
    Olsson, Fredrik
    von Fieandt, Linus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Bednarcik, Jozef
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl2018In: Scientific Reports, E-ISSN 2045-2322, Vol. 8, no 1, article id 2525Article in journal (Refereed)
    Abstract [en]

    The low cost, rare earth free τ-phase of MnAl has high potential to partially replace bonded Nd2Fe14B rare earth permanent magnets. However, the τ-phase is metastable and it is experimentally difficult to obtain powders suitable for the permanent magnet alignment process, which requires the fine powders to have an appropriate microstructure and high τ-phase purity. In this work, a new method to make high purity τ-phase fne powders is presented. A high purity τ-phase Mn0.55Al0.45C0.02 alloy was synthesized by the drop synthesis method. The drop synthesized material was subjected to cryo milling and followed by a fash heating process. The crystal structure and microstructure of the drop synthesized, cryo milled and flash heated samples were studied by X-ray in situ powder diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy and electron backscatter diffraction. Magnetic properties and magnetic structure of the drop synthesized, cryo milled, flash heated samples were characterized by magnetometry and neutron powder diffraction, respectively. The results reveal that the 2 and 4hours cryo milled and flash heated samples both exhibit high τ-phase purity and micron-sized round particle shapes. Moreover, the fash heated samples display high saturation magnetization as well as increased coercivity.

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  • 27.
    Fang, Hailiang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Kontos, Sofia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ångstrom, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Directly obtained tau-phase MnAl, a high performance magnetic material for permanent magnets2016In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 237, p. 300-306Article in journal (Refereed)
    Abstract [en]

    The metastable tetragonal iota-phase has been directly obtained from casting Mn0.54Al0.46 and (Mn0.55Al0.45)(100)C-2 using the drop synthesis method. The as-casted samples were ball milled to decrease the particle size and relaxed at 500 degrees C for 1 h. The phase composition, crystallographic parameters, magnetic properties and microstructure were systematically studied. The results reveal that the iota-phase could be directly obtained from drop synthesis. The highest M-s of 117 emu/g was achieved in the (Mn0.55Al0.45)(100)C-2 where the iota-phase was stabilized by doping with carbon. Carbon doping increased the c/a ratio of the tau-phase as it occupies specific interstitial positions (1/2, 1/2, 0) in the structure. Furthermore, ball milling increases the coercivity (H-c) at the expense of a decrease in magnetic saturation (M-s). The increase in coercivity is explained by a decrease of grain size in conjunction with domain wall pinning due to defects introduced during the ball milling process.

  • 28.
    Fang, Hailiang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Li, Jiheng
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Univ Sci & Technol Beijing, State Key Lab Adv Met & Mat, Beijing, Peoples R China.
    Shafeie, Samrand
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hedlund, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Ekström, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gómez, Cesar Pay
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Bednarcik, Jozef
    Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22603 Hamburg, Germany.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Insights into phase transitions and magnetism of MnBi crystals synthesized from self-flux2019In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 781, p. 308-314Article in journal (Refereed)
    Abstract [en]

    To effectively synthesize high purity ferromagnetic low temperature phase (LTP) MnBi with optimal microstructure is still a challenge that needs to be overcome for the system to reach its full potential. Here, the phase transitions and magnetic properties of MnBi crystals are reported. The phase transition between the low and high temperature structure of MnBi was systematically investigated at different heating/cooling rates using in situ synchrotron radiation X-ray diffraction. The material crystallizes in a layered hexagonal structure giving a platelike microstructure. The magnetic characterization of the crystals reveal that the saturation magnetization varies from 645 kA/m at 50 K to 546 kA/m at 300 K. Magnetization measurements also show that the sample upon heating becomes non-magnetic and transforms to the high temperature phase (HTP) at similar to 640 K, and that it regains ferromagnetic properties and transforms back to the LTP at similar to 610 K upon subsequent cooling.

  • 29.
    Gebresenbut, Girma
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Andersson, Mikael Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Beran, Pr™emysl
    Manuel, Pascal
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Gomez, Cesar Pay
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Long range ordered magnetic and atomic structures of the quasicrystal approximant in the Tb-Au-Si system2014In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 26, no 32, p. 322202-Article in journal (Refereed)
    Abstract [en]

    The atomic and magnetic structure of the 1/1 Tb(14)Au(70)Si(16) quasicrystal approximant has been solved by combining x-ray and neutron diffraction data. The atomic structure is classified as a Tsai-type 1/1 approximant with certain structural deviations from the prototype structures; there are additional atomic positions in the so-called cubic interstices as well as in the cluster centers. The magnetic property and neutron diffraction measurements indicate the magnetic structure to be ferrimagnetic-like below 9 K in contrast to the related Gd(14)Au(70)Si(16) structure that is reported to be purely ferromagnetic.

  • 30.
    Gebresenbut, Girma H.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Andersson, Mikael S.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Gomez, Cesar Pay
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tailoring Magnetic Behavior in the Tb-Au-Si Quasicrystal Approximant System2016In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 55, no 5, p. 2001-2008Article in journal (Refereed)
    Abstract [en]

    A novel synthesis method, "arc-melting-self-flux", has been developed and a series of five Tsai-type 1/1 approximant crystals in the Tb-Au-Si system have been synthesized. The synthesis method, by employing a temperature program which oscillates near the melting and nucleation points of the approximants, has provided high-quality and large single crystals in comparison to those obtained from the standard arc-melting-annealing and self-flux methods. The atomic structures of the approximants have been determined from single-crystal X-ray diffraction data and described using concentric atomic clusters with icosahedral symmetry. The compounds are nearly isostructural with subtle variations; two types of atomic clusters which mainly vary at their cluster centers are observed. One type contains a Tb site at the center, and the other contains a disordered tetrahedron decorated with Au/Si mixed sites. Both cluster types can be found coexisting in the approximants. The compounds have different average weighted ratios of central Tb to disordered tetrahedron in the bulk material. Furthermore, a strategy for chemically tuning magnetic behavior is presented. Magnetic property measurements on the approximants revealed that the magnetic transition temperature (T-c) decreases as the occupancy of the central Tb site increases. T-c decreased from 11.5 K for 0% occupancy of the central Tb to 8 K for 100% occupancy. Enhanced magneto crystalline anisotropy is observed for the approximants with higher central Tb occupancy in comparison to their low central Tb occupancy counterparts. Hence, the previously reported "ferrimagnetic-like" magnetic structure model remains valid.

  • 31.
    Gebresenbut, Girma Hailu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Andersson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Qureshi, Navid
    Institut Laue Langevin, 6 rue Jules Horowitz, Boîıte Postale 156, F-38042 Grenoble, France.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Pay Gómez, Cesar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Single crystal growth, structure determination and magnetic behavior of RE-Au-Si quasicrystal approximants (RE = Ho and Tb)Manuscript (preprint) (Other academic)
  • 32.
    Ghorai, Sagar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Cedervall, Johan
    Clulow, Rebecca
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Huang, Shuo
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Shtender, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Delczeg-Czirjak, Erna K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Vitos, Levente
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Site-specific atomic substitution in a giant magnetocaloric Fe2P-type system2023In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 107, no 10, article id 104409Article in journal (Refereed)
    Abstract [en]

    Giant magnetocaloric (GMC) materials constitute a requirement for near room temperature magnetic refrigeration. (Fe,Mn)2(P,Si) is a GMC compound with strong magnetoelastic coupling. The main hindrance towards application of this material is a comparably large temperature hysteresis, which can be reduced by metal site substitution with a nonmagnetic element. However, the (Fe,Mn)2(P,Si) compound has two equally populated metal sites, the tetrahedrally coordinated 3f and the pyramidally coordinated 3g sites. The magnetic and magnetocaloric properties of such compounds are highly sensitive to the site specific occupancy of the magnetic atoms. Here we have attempted to study separately the effect of 3f and 3g site substitution with equal amounts of vanadium. Using formation energy calculations, the site preference of vanadium and its influence on the magnetic phase formation are described. A large difference in the isothermal entropy change (as high as 44\%) with substitution in the 3f and 3g sites is observed. The role of the lattice parameter change with temperature and the strength of the magnetoelastic coupling on the magnetic properties are highlighted.

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  • 33.
    Ghorai, Sagar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Huang, Shuo
    Clulow, Rebecca
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Skini, Ridha
    Shtender, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Delczeg-Czirjak, Erna Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Vitos, Levente
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Magnetocaloric properties of nonstoichiometric Fe2P-type intermetallics near room temperatureManuscript (preprint) (Other academic)
  • 34.
    Ghorai, Sagar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Shtender, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Delczeg-Czirjak, Erna Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Vieira, Rafael Martinho
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Herper, Heike C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Magneto-structural coupling strength dependent giant magnetocaloric effect in (Mn,Fe)NiSi-systemManuscript (preprint) (Other academic)
  • 35.
    Ghorai, Sagar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Vieira, Rafael Martinho
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Shtender, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Delczeg-Czirjak, Erna Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Herper, Heike C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Björkman, Torbjörn
    Simak, Sergei I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics III. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics V. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Surface Biotechnology. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics III. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics V. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Giant magnetocaloric effect in the (Mn,Fe)NiSi-system2023Manuscript (preprint) (Other academic)
    Abstract [en]

    The search for energy-efficient and environmentally friendly cooling technologies is a key driver for the development of magnetic refrigeration based on the magnetocaloric effect (MCE). This phenomenon arises from the interplay between magnetic and lattice degrees of freedom that is strong in certain materials, leading to a change in temperature upon application or removal of a magnetic field. Here we report on a new material, Mn1−xFexNiSi0.95Al0.05, with an exceptionally large isothermal entropy at room temperature. By combining experimental and theoretical methods we outline the microscopic mechanism behind the large MCE in this material. It is demonstrated that the competition between the Ni2In-type hexagonal phase and the MnNiSi-type orthorhombic phase, that coexist in this system, combined with the distinctly different magnetic properties of these phases, is a key parameter for the functionality of this material for magnetic cooling.

  • 36.
    Hedlund, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edström, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Materials Theory, ETH Zürich.
    Werwinski, Miroslaw
    Polish Academy of Sciences.
    Kontos, Sofia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Örebro University.
    Rusz, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Magnetic properties of the Fe5SiB2−Fe5PB2 system2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 9, article id 094433Article in journal (Refereed)
    Abstract [en]

    The magnetic properties of the compound Fe5Si1−xPxB2 have been studied, with a focus on the Curie temperature TC, saturation magnetization MS, and magnetocrystalline anisotropy. Field and temperature dependent magnetization measurements were used to determine TC(x) and MS(x). The saturation magnetization at 10 K (300 K) is found to monotonically decrease from 1.11MA/m (1.03MA/m) to 0.97MA/m (0.87MA/m), as x increases from 0 to 1. The Curie temperature is determined to be 810 and 615 K in Fe5SiB2 and Fe5PB2, respectively. The highest TC is observed for x=0.1, while it decreases monotonically for larger x. The Curie temperatures have also been theoretically determined to be 700 and 660 K for Fe5SiB2 and Fe5PB2, respectively, using a combination of density functional theory and Monte Carlo simulations. The magnitude of the effective magnetocrystalline anisotropy was extracted using the law of approach to saturation, revealing an increase with increasing phosphorus concentration. Low-field magnetization vs temperature results for x=0,0.1,0.2 indicate that there is a transition from easy-axis to easy-plane anisotropy with decreasing temperature.

  • 37.
    Hedlund, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Rosenqvist Larsen, Simon
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Shtender, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Influence of Mn content on the magnetic properties of the hexagonal Mn (Co,Ge)2 phase2023In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 233, article id 115534Article in journal (Refereed)
    Abstract [en]

    Herein, we report on the effect of Mn content on the magnetic properties of the hexagonal Mn(Co,Ge)2 with composition Mn36+xCo49-xGe15.This compound was previously described as Mn2Co3Ge (MgZn2-type structure), but later as Mn(Co,Ge)2 with its own structure type, all samples in this work follow the same superstructure model. Samples were synthesized by induction melting, the crystal structures were evaluated using a combination of X-ray diffraction together with scanning electron microscopy equipped and an energy dispersive X-ray spectroscopy detector. The Curie temperature (TC) is shifted towards lower temperature as the Mn content is increased. On the other hand, the spin reorientation temperature (TSRT) increases and the magnetic moment decreases as the Mn content is increased. The magnetocaloric properties were investigated for the x = 1 alloy, Mn37Co48Ge15. It was found that the isothermal entropy change is 2 J kg−1 K−1 at room temperature for an applied field of 5 T.

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  • 38.
    Hudl, Matthias
    et al.
    Department of Materials, ETH Zürich; KTH Royal Institute of Technology, ICT Materials Physics.
    Campanini, Donato
    Department of Physics, Stockholm University.
    Caron, Luana
    Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, TU Delft.
    Höglin, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Rydh, Andreas
    Department of Physics, Stockholm University.
    Thermodynamics around the first-order ferromagnetic phase transition of Fe2P single crystals2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 14, p. 144432-Article in journal (Refereed)
    Abstract [en]

    The specific heat and thermodynamics of Fe2P single crystals around the first-order paramagnetic to ferromagnetic (FM) phase transition at TC = 217K are empirically investigated. The magnitude and direction of the magnetic field relative to the crystal axes govern the derived H-T phase diagram. Strikingly different phase contours are obtained for fields applied parallel and perpendicular to the c axis of the crystal. In parallel fields, the FM state is stabilized, while in perpendicular fields the phase transition is split into two sections, with an intermediate FM phase where there is no spontaneous magnetization along the c axis. The zero-field transition displays a textbook example of a first-order transition with different phase stability limits on heating and cooling. The results have special significance since Fe2P is the parent material to a family of compounds with outstanding magnetocaloric properties.

  • 39.
    Hudl, Matthias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Delczeg-Czirjak, Erna-Krisztina
    Dept of Materials Science and Engineering, Royal Institute of Technology, Stockholm.
    Höglin, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Strongly enhanced magnetic moments in ferromagnetic FeMnP0.5Si0.52011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 15, p. 152502-Article in journal (Refereed)
    Abstract [en]

    The compound FeMnP(0.5)Si(0.5) has been studied by magnetic measurements, Mossbauer spectroscopy, and electronic structure and total energy calculations. An unexpectedly high magnetic hyperfine field for Fe atoms located at the tetrahedral Me(1) site in the Fe(2)P structure is found, The saturation moment derived from magnetic measurements corresponds to 4.4 mu(B)/f.u. at low temperatures, a value substantially higher than previously reported, but in accordance with the results from our electron structure calculations, This high saturation moment and the tunable first order ferromagnetic transition make the Fe(2-x)Mn(x)P(1-y)Si(y), system promising for magnetocaloric applications.

  • 40.
    Hudl, Matthias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Björkman, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Delczeg-Czirjak, Erna-Krisztina
    School of Industrial Engineering and Management, Royal Institute of Technology, Stockholm.
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Order–disorder induced magnetic structures of FeMnP0.75Si0.252011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 13, article id 134420Article in journal (Refereed)
    Abstract [en]

    We report on the synthesis and structural characterization of the magnetocaloric FeMnP0.75Si0.25 compound. Two types of samples (as quenched and annealed) were synthesized and characterized structurally and magnetically. We have found that minute changes in the degree of crystallographic order causes a large change in the magnetic properties. The annealed sample, with higher degree of order is antiferromagnetic with a zero net moment. The as-quenched sample has a net moment of 1.26 μB /f.u. and ferrimagnetic-like behavior. Theoretical calculations give rather large values for the Fe and Mn magnetic moments, both when occupied on the tetrahedral and pyramidal lattice site. The largest being the Mn moment for the pyramidal site reaches values as high as 2.8 μB /atom.

  • 41.
    Höglin, Viktor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Mikael Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sarkar, Tapati
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hudl, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. ICT Materials Physics, KTH Royal Institute of Technology.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Phase diagram, structures and magnetism of the FeMnP1-xSix-system2015In: RSC Advances, E-ISSN 2046-2069, Vol. 5, no 11, p. 8278-8284Article in journal (Refereed)
    Abstract [en]

    The magnetic properties of the (Fe,Mn)2(P,Si)-system have been shown to be readily manipulated by small changes in composition. This study surveys the FeMnP1−xSix-system (0.00 ≤ x ≤ 1.00) reporting sample syntheses and investigations of crystallographic and magnetic properties using X-ray powder diffraction and magnetic measurements. Two single phase regions exist: the orthorhombic Co2P-type structure (x < 0.15) and the Fe2P-type structure (0.24 ≤ x < 0.50). Certain compositions have potential for use in magnetocaloric applications.

  • 42.
    Höglin, Viktor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Mikael Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sarkar, Tapati
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Irreversible structure change of the as prepared FeMnP1−xSix-structure on the initial cooling through the curie temperature2015In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 374, p. 455-458Article in journal (Refereed)
    Abstract [en]

    FeMnP0.75Si0.25 experiences a first order para- to ferromagnetic transition at about 200 K. In common with some other alloy compositions crystallizing in the Fe2P structure, the magnetic transition of the as prepared alloy occurs at a lower temperature than on subsequent cooling events. This virgin effect is found to be accompanied by a magnetostrictively induced irreversible structure change that persists on succeeding cooling heating cycles. These findings provide means to understand and control the thermal hysteresis of the (Fe1-xMnx)(2)P1-ySiy alloy system which is a promising material class for use in magnetocaloric refrigerators.

  • 43.
    Höglin, Viktor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hudl, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. ICT Materials Physics, KTH Royal Institute of Technology.
    Caron, Luana
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, TUDelft.
    Beran, Premysl
    Nuclear Physics Institute, Academy of Sciences of the Czech Republic.
    Sørby, Magnus H.
    Physics Department, Institute for Energy Technology.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Detailed study of the magnetic ordering in FeMnP0.75Si0.252015In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 221, p. 240-246Article in journal (Refereed)
    Abstract [en]

    Magnetic and crystallographic properties of FeMnP0.75Si0.25 in the hexagonal Fe2P-type structure have been investigated by X-ray powder diffraction, neutron powder diffraction and magnetic measurements. The room temperature diffractograms reveal co-existence of two distinct structural phases in the samples with small, but significant, differences only in the unit cell dimensions. The volume ratio between the two phases is governed by the annealing conditions. One of the phases orders ferromagnetically (TC = 250 K) and the other in an incommensurate antiferromagnetic structure at low temperatures (qx = 0.363(1), TN = 150 K).

  • 44.
    Höglin, Viktor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Hudl, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Beran, Premysl
    Nuclear Physics Institute, Academy of Sciences of the Czech Republic.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    The crystal and magnetic structure of the magnetocaloric compound FeMnP0.5Si0.52011In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 184, no 9, p. 2434-2438Article in journal (Refereed)
    Abstract [en]

    The crystal and magnetic structure of the magnetocaloric compound FeMnP0.5Si0.5 has been studied by means of neutron and X-ray powder diffraction. Single phase samples of nominal composition FeMnP0.5Si0.5 have been prepared by the drop synthesis method. The compound crystallizes in the Fe2P-type structure (P-62m) with the magnetic moments aligned along the a-axis. It is found that the Fe atoms are mainly situated in the tetrahedral 3g site while the Mn atoms prefer the pyramidal 3f position. The material is ferromagnetic (TC=382 K) and at 296 K the total magnetic moment is 4.4 µB/f.u. It is shown that the magnetic moment in the 3f site is larger (2.5 µB) than in the 3g site (1.9 µB).

  • 45.
    Höglin, Viktor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Ångström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Mikael Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Balmes, Olivier
    MAX IV Laboratory, Lund University.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sample cell for in-field X-ray diffraction experiments2015In: Results in Physics, ISSN 2211-3797, Vol. 5, p. 53-54Article in journal (Refereed)
    Abstract [en]

    A sample cell making it possible to perform synchrotron radiation X-ray powder diffraction experiments in a magneticfield of 0.35 T has been constructed. The device is an add-on to an existing sample cell and contains a strong permanentmagnet of NdFeB-type. Experiments have shown that the setup is working satisfactory making it possible to performin-field measurements.

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  • 46.
    Ivanov, Sergey
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Karpov Inst Phys Chem, Ctr Mat Sci, Vorontsovo Pole 10, Moscow Russia.
    Andersson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Bazuev, G. V.
    Russian Acad Sci, Inst Solid State Chem, Ural Branch, Ekaterinburg 620990, Russia.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Temperature-dependent structural and magnetic properties of R2MMnO6 double perovskites (R=Dy, Gd; M=Ni, Co)2018In: Journal of materials science. Materials in electronics, ISSN 0957-4522, E-ISSN 1573-482X, Vol. 29, no 21, p. 18581-18592Article in journal (Refereed)
    Abstract [en]

    The structural and magnetic properties of the Dy2CoMnO6, Dy2NiMnO6 and Gd2CoMnO6 double perovskites are investigated using X-ray powder diffraction and squid magnetometry. The materials adopt an orthorhombic structure (space ground Pnma) with disordered Co(Ni)/Mn cations, and exhibit ferrimagnetic transitions near T(C)85, 95, and 115K respectively. T-C was found to monotonously depend on the orthorhombic distortion (a-c)/(a+c) of the compounds. The crystal structure of the compounds was investigated as a function of temperature (16-1100K range), evidencing changes in the BO6 octahedron near T-C. The magnetic entropy changes are estimated for comparison of the magnetocaloric properties to those from literature.

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  • 47.
    Ivanov, Sergey
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Karpov Inst Phys Chem, Ctr Mat Sci, Vorontsovo Pole 10, Moscow 105064, Russia.
    Beran, Premysl
    CAS, Inst Nucl Phys, Rez, Czech Republic.
    Bush, Alexandr A.
    Moscow Technol Univ, Moscow 119454, Russia.
    Sarkar, Tapati
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Shafeie, Samrand
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Wang, Duo
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Kvashnin, Yaroslav
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Tellgren, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Cation ordering, ferrimagnetism and ferroelectric relaxor behavior in Pb(Fe1-xScx)(2/3)W1/3O3 solid solutions2019In: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 92, no 8, article id 163Article in journal (Refereed)
    Abstract [en]

    Ceramic samples of the multiferroic perovskite Pb(Fe1-xScx)(2/3)W1/3O3 with 0 <= x <= 0.4 have been synthesized using a conventional solid-state reaction method, and investigated experimentally and theoretically using first-principle calculations. Rietveld analyses of joint synchrotron X-ray and neutron diffraction patterns show the formation of a pure crystalline phase with cubic (Fm3(_)m) structure with partial ordering in the B-sites. The replacement of Fe by Sc leads to the increase of the cation order between the B and B '' sites. As the non-magnetic Sc3+ ions replace the magnetic Fe3+ cations, the antiferromagnetic state of PbFe2/3W1/3O3 is turned into a ferrimagnetic state reflecting the different magnitude of the magnetic moments on the B ' and B '' sites. The materials remain ferroelectric relaxors with increasing Sc content. Results from experiments on annealed and quenched samples show that the cooling rate after high temperature annealing controls the degree of cationic order in Pb(Fe1-xScx)(2/3)W1/3O3 and possibly also in the undoped PbFe2/3W1/3O3.

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  • 48.
    Jacobsson, Jesper T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Fjällström, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Sahlberg, Martin Häggblad
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    A monolithic device for solar water splitting based on series interconnected thin film absorbers reaching over 10% solar-to-hydrogen efficiency2013In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 6, no 12, p. 3676-3683Article in journal (Refereed)
    Abstract [en]

    Efficient production of hydrogen from solar energy is anticipated to be an important component in a future sustainable post-carbon energy system. Here we demonstrate that series interconnected absorbers in a PV-electrolysis configuration based on the compound semiconductor CIGS, CuInxGa1-xSe2, are a highly interesting concept for solar water splitting applications. The band gap energy of CIGS can be adjusted to a value close to optimum for efficient absorption of the solar spectrum, but is too low to drive overall water splitting. Therefore we connect three cells in series, into a monolithic device, which provides sufficient driving force for the full reaction. Integrated with a catalyst this forms a stable PV/photo-electrochemical device, which when immersed in water reaches over 10% solar-to-hydrogen efficiency for unassisted water splitting. The results show that series interconnected device concepts, which enable use of a substantial part of the solar spectrum, provide a simple route towards highly efficient water splitting and could be used also for other solar absorbers with similar electro-optical properties. We discuss how the efficiency could be increased for this particular device, as well as the general applicability of the concepts used in this work. We also briefly discuss advantages and disadvantages of photo-electrochemical cells in relation to PV-electrolysis with respect to our results.

  • 49.
    Kamali, Saeed
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics III.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wäppling, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Magnetic and interface properties of Fe0.82Ni0.18/Co(001) superlattices2011In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 23, no 5, p. 055301-Article in journal (Refereed)
    Abstract [en]

    The thickness dependence of the Fe magnetic hyperfine field and the interfacial intermixing of Fe0.82Ni0.18/Co superlattices, with the same thickness for FeNi and Co layers, have been investigated. A local concentration model using the magnetic hyperfine field values from the [Fe0.82Ni0.18](1-x)Co-x alloys has been used to interpret the field distribution in the superlattices and the Co concentration profiles over the superlattices. A relationship between the Fe magnetic hyperfine field and the Fe magnetic moment has been determined for the unordered [Fe0.82Ni0.18](1-x)Co-x and Fe1-xCox alloys. The magnetic hyperfine fields have been explained using two Fermi contact terms: (i) the core electron term proportional to the Fe magnetic moment with a proportionality constant of -13 T/mu B and (ii) a valence electron term linearly dependent on the Co concentration. The direction of the magnetic moments is found to be in the sample plane except for the 1/1 superlattice, where an angle of about 45 degrees is found.

  • 50. Kamali, Saeed
    et al.
    Shahmiri, Nesa
    Garitaonandia, Jose S.
    Ångström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Effect of mixing tool on magnetic properties of hematite nanoparticles prepared by sol-gel method2013In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 534, p. 260-264Article in journal (Refereed)
    Abstract [en]

    X-ray diffraction, Mossbauer and magnetization measurements have been performed on hematite nanoparticles, prepared by sol-gel method, to study the effect of the mixing tools used in the preparation on their magnetic properties. It has been shown that the mixing tool, i.e. magnetic or mechanical, has a crucial effect on the magnetic behaviors of magnetic nanoparticles. Furthermore, the degree of purity of nitrogen gas used in the preparation process also plays a minor role in magnetic properties of such nanoparticles.

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