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  • 1.
    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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  • 2.
    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
    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, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of Mn/Co ratio on the magnetic properties of the hexagonal Mn(Co,Ge)2 phaseManuscript (preprint) (Other academic)
  • 3.
    Larsen, Simon R.
    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.
    Stopfel, Henry
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Karlsson, Dennis
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Christensen, Christian K.
    DESY, Photon Sci Div, Notkestr 85, D-22607 Hamburg, Germany.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Cedervall, Johan
    Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden.
    Magnetic properties and thermal stability of B2 and bcc phases in AlCoCrFeMnxNi2021In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 861, article id 158450Article in journal (Refereed)
    Abstract [en]

    Alloys of AlCoCrFeMnxNi (x = 0.0, 0.04, 0.08, 0.12 and 0.16) have been synthesized through arc–melting and gas atomisation (x = 0.0 and 0.16) to investigate the effect of Mn additions to AlCoCrFeNi. Here, the structure, magnetic properties and the thermal stability of the alloys is presented. Electron microscopy confirmed the elemental composition and revealed the microstructure to consist of two spinodally decomposed phases. Rietveld analysis of standard powder X-ray diffraction showed the arc-melted samples consisted of two phases, a B2 phase and a bcc phase while the gas atomised powders consisted of a single-phased B2 structure. Magnetic measurements revealed an increase in the saturation magnetisation at room temperature by 68% for AlCoCrFeMnNi compared to AlCoCrFeNi. The thermal stability of the alloys was investigated using magnetometry, differential scanning calorimetry and in–situ X-ray diffraction, which showed that an increase in Mn content adversely effected the thermal stability of the alloy.

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  • 4.
    Larsen, Simon R.
    et al.
    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.
    Hedlund, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Delczeg-Czirjak, Erna K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Beran, Premysl
    Nuclear Physics Institute, ASCR, Hlavni 130, 25068 Rez, Czech Republic; European Spallation Source ESS ERIC, Box 176, 221 00, Lund, Sweden.
    Cedervall, Johan
    Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden.
    Vishina, Alena
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hansen, Thomas C.
    Institut Laue-Langevin, 71 avenue des Martyrs, 38000 Grenoble, France.
    Herper, Heike C.
    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.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. School of Science and Technology, Örebro University, SE-701 82 Örebro, Sweden.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Revealing the Magnetic Structure and Properties of Mn(Co,Ge)22022In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 61, no 44, p. 17673-17681Article in journal (Refereed)
    Abstract [en]

    The atomic and magnetic structures of Mn(Co,Ge)2 are reported herein. The system crystallizes in the space group P63/mmc as a superstructure of the MgZn2-type structure. The system exhibits two magnetic transitions with associated magnetic structures, a ferromagnetic (FM) structure around room temperature, and an incommensurate structure at lower temperatures. The FM structure, occurring between 193 and 329 K, is found to be a member of the magnetic space group P63/mmc′. The incommensurate structure found below 193 K is helical with propagation vector k = (0 0 0.0483). Crystallographic results are corroborated by magnetic measurements and ab initio calculations.

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  • 5.
    Rosenqvist Larsen, Simon
    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.
    Clulow, Rebecca
    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.
    Delczeg-Czirjak, Erna Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Cedervall, Johan
    Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden.;Rutherford Appleton Lab, ISIS Pulsed Neutron & Muon Facil, Harwell Campus, Didcot OX11 0QX, England..
    Magnetism and magnetic structure determination of a selected (Mn,Co)(23)B-6-compound2022In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 905, article id 164225Article in journal (Refereed)
    Abstract [en]

    The vast compositional space in cubic Cr23C6-type compounds (space group Fm3 over line m) opens up possibilities to tune properties by performing substitutions. In this study, the magnetic properties have been explored in a selected (Mn,Co)(23)B-6-compound by the means of synchrotron X-ray diffraction, neutron powder diffraction, magnetometry and electronic structure calculations. Refinements of a structural model based on combined X-ray and neutron diffraction data revealed mixed metal occupancies at all metal positions. However, two sites were richer in Co and the other two showed an abundance of Mn. The magnetic characteristics showed a ferrimagnetic structure below 550 K, with the magnetic moments aligned along the crystallographic c-direction and the magnetic moments on corner atoms having an opposite direction compared to the rest, within the magnetic space group I 4 mm m. The total magnetic moments extracted from magnetometry and neutron diffraction data gave similar values at 6 K, 20.1 and 18.2 mu(B)/f.u., respectively. Results from electronic structure calculations are in reasonable agreement with the experimental findings.& nbsp;(C) 2022 The Author(s). Published by Elsevier B.V. CC_BY_4.0

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  • 6.
    Shtender, Vitalii
    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.
    Rosenqvist Larsen, Simon
    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.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Structural and magnetic properties of new members of the 3:29 phase from the Ce-Fe-Mn system and 1:11 from the Ce-Co-Mn2021In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 855, article id 157435Article in journal (Refereed)
    Abstract [en]

    The Ce–Fe–Mn and Ce–Co–Mn systems have been re-visited with the intent of finding new potential phases for application as permanent magnets. Two new ternary compounds, Ce3(Fe0.638Mn0.362)29 (Nd3(Fe,Ti)29-type, space group P21/c, No. 14, Pearson Symbol mP128) and CeCo8Mn3 (Ce(Ni,Mn)11-type, space group P4/mbm, No. 127, Pearson Symbol tP24) have been discovered in the compositional range where the Ce2(T,Mn)17 (T = Fe, Co) phases are expected to exist with a (H)–Th2Ni17-type structure (space group P63/mmc, No. 194, Pearson Symbol hP38). Detailed investigations of the crystal structures have been performed using X-ray powder diffraction (XRPD) with supporting energy-dispersive X-ray (EDS) analysis. Compositions of the new compounds have been defined based on the EDS analysis as follows: Ce9.7Fe57.5Mn32.8 and Ce9.2Co65.2Mn25.6. A short discussion on the crystal structure peculiarities of the 1:5, 1:11, 1:12, 2:17 and 3:29 compounds in the Ce–T–Mn (T = Fe, Co, Ni, Cu) systems has been made. We present magnetic measurements on selected representatives of the studied phases. The most interesting being the Ce3(Fe0.638Mn0.362)29 phase which has a transition temperature well above room temperature. CeNi4.95Mn6.05 and CeCo8Mn3 exhibits properties characteristic of a canted antiferromagnetic state.

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  • 7.
    Shtender, Vitalii
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    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.
    Variants of the X-phase in the Mn-Co-Ge system2021In: ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY, ISSN 2053-2296, Vol. 77, p. 176-180Article in journal (Refereed)
    Abstract [en]

    We report two new variants of the X-phase (orthorhombic, space group Pnnm) derived from the Mn-Co-Ge system. Two compositionally related crystals were investigated by means of single-crystal X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The Mn14.9Co15.5Ge6.6 and Mn14Co16.2Ge6.8 intermetallic compounds are part of the homogeneity region of the X-phase and adopt the Mn-14(Mn0.11Co0.64Si0.25)(23) structure type. The composition obtained from refinement of the XRD data is in agreement with the EDS results. In the present study, chemical disorder was only detected on the 8h positions. The ordering is compared with other members of the X-phase family and shows that the degree of disordering depends on the chemical composition. No completely ordered variants of the X-phase have yet been reported.

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  • 8.
    Vishina, Alena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hedlund, Daniel
    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 K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Larsen, Simon R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Vekilova, Olga Yu.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden.
    Huang, Shuo
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden.
    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.
    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.
    Herper, Heike C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Data-driven design of a new class of rare-earth free permanent magnets2021In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 212, article id 116913Article in journal (Refereed)
    Abstract [en]

    A new class of rare-earth-free permanent magnets is proposed. The parent compound of this class is Co3Mn2Ge, and its discovery is the result of first principles theory combined with experimental synthesis and characterisation. The theory is based on a high-throughput/data-mining search among materials listed in the ICSD database. From ab-initio theory of the defect free material it is predicted that the saturation magnetization is 1.71 T, the uniaxial magnetocrystalline anisotropy is 1.44 MJ/m3, and the Curie temperature is 700 K. Co3Mn2Ge samples were then synthesized and characterised with respect to structure and magnetism. The crystal structure was found to be the MgZn2-type, with partial disorder of Co and Ge on the crystallographic lattice sites. From magnetization measurements a saturation polarization of 0.86 T at 10 K was detected, together with a uniaxial magnetocrystalline anisotropy constant of 1.18 MJ/m3, and the Curie temperature of TC = 359 K. These magnetic properties make Co3Mn2Ge a very promising material as a rare-earth free permanent magnet, and since we can demonstrate that magnetism depends critically on the amount of disorder of the Co and Ge atoms, a further improvement of the magnetism is possible. We demonstrate here that the class of compounds based on T3Mn2X (T = Co or alloys between Fe and Ni; X = Ge, Al or Ga) in the MgZn2 structure type, form a new class of rare-earth free permanent magnets with very promising performance.

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