Logo: to the web site of Uppsala University

uu.sePublications from Uppsala University
Change search
Link to record
Permanent link

Direct link
Publications (10 of 22) Show all publications
Ghorai, S., Hedlund, D., Kapuscinski, M. & Svedlindh, P. (2023). A setup for direct measurement of the adiabatic temperature change in magnetocaloric materials. IEEE Transactions on Instrumentation and Measurement, 72, 1-9
Open this publication in new window or tab >>A setup for direct measurement of the adiabatic temperature change in magnetocaloric materials
2023 (English)In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 72, p. 1-9Article in journal (Refereed) Published
Abstract [en]

In order to find a highly efficient, environmentally-friendly magnetic refrigerant, direct measurements of the adiabatic temperature change ΔTadb are required. Here, in this work, a simple setup for the ΔTadb measurement is presented. Using a permanent magnet Halbach array with a maximum magnetic field of 1.8 T and a rate of magnetic field change of 5 T/s, accurate determination of ΔTadb is possible in this system. The operating temperature range of the system is from 100 to 400 K, designed for the characterization of materials with potential for room temperature magnetic refrigeration applications. Using the setup, ΔTadb of a first-order and two second-order compounds have been studied. Results from the direct measurement for the first-order compound have been compared with ΔTadb calculated from the temperature and magnetic field-dependent specific heat data. By comparing results from direct and indirect measurements, it is concluded that for a reliable characterization of the magnetocaloric effect (MCE), direct measurement of ΔTadb should be adopted.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-487263 (URN)10.1109/TIM.2023.3272387 (DOI)000991806800037 ()
Funder
Swedish Foundation for Strategic Research, EM−16−0039
Available from: 2022-10-26 Created: 2022-10-26 Last updated: 2023-08-14Bibliographically approved
Hedlund, D., Rosenqvist Larsen, S., Sahlberg, M., Svedlindh, P. & Shtender, V. (2023). Influence of Mn content on the magnetic properties of the hexagonal Mn (Co,Ge)2 phase. Scripta Materialia, 233, Article ID 115534.
Open this publication in new window or tab >>Influence of Mn content on the magnetic properties of the hexagonal Mn (Co,Ge)2 phase
Show others...
2023 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 233, article id 115534Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Permanent magnets, Intermetallic compound, Synthesis, Magnetocalloric properties, Crystal structure
National Category
Condensed Matter Physics Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-504952 (URN)10.1016/j.scriptamat.2023.115534 (DOI)001001481400001 ()
Funder
Swedish Foundation for Strategic Research, EM16-0039Swedish Research Council, 2019-00207
Available from: 2023-06-19 Created: 2023-06-19 Last updated: 2023-06-19Bibliographically approved
Shtender, V., Paul-Boncour, V., Denys, R., Hedlund, D., Svedlindh, P. & Zavaliy, I. (2022). Impact of the R and Mg on the structural, hydrogenation and magnetic properties of R3-xMgxCo9 (R = Pr, Nd, Tb and Y) compounds. Materials research bulletin, 156, Article ID 111981.
Open this publication in new window or tab >>Impact of the R and Mg on the structural, hydrogenation and magnetic properties of R3-xMgxCo9 (R = Pr, Nd, Tb and Y) compounds
Show others...
2022 (English)In: Materials research bulletin, ISSN 0025-5408, E-ISSN 1873-4227, Vol. 156, article id 111981Article in journal (Refereed) Published
Abstract [en]

R2MgCo9 (R = Pr, Nd, Tb and Y) compounds have been synthesized by a powder sintering method and the corresponding hydrides have been prepared by a solid gas method. Their crystal structures and magnetic properties have been systematically studied. X-ray diffraction analysis showed that all R2MgCo9 compounds belong to the PuNi3-type structure. The elements Tb, Y, Nd, Pr yield a lowering of the equilibrium pressure which correlates well with the increase in cell volume. The R2MgCo9H(D)x (R = Pr, Nd, Tb and Y; (9.4 <= x <= 12)) hydrides (deuterides) preserve the PuNi3-type structure with hydrogenation-induced volume expansion ranging from 14.7 to 19.6%. The substitution of deuterium for hydrogen in R2MgCo9-(H,D)(2) (R = Tb and Y) prevents fast desorption at room temperature and ambient pressure. As for the magnetic properties, all the studied interme-tallic compounds show ferromagnetic or ferrimagnetic behavior, and in some cases a temperature dependent spin reorientation. Hydrogen insertion reduces the magnetization and decreases the magnetic ordering temperature (TC), whereas Mg for R substitution increases TC.

Place, publisher, year, edition, pages
ElsevierElsevier BV, 2022
Keywords
Rare e arth compounds, Magnesium compounds, Metal hydrides, Crystal structures, Magnetic properties
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-483854 (URN)10.1016/j.materresbull.2022.111981 (DOI)000843629300005 ()
Available from: 2022-09-05 Created: 2022-09-05 Last updated: 2024-01-15Bibliographically approved
Clulow, R., Hedlund, D., Vishina, A., Svedlindh, P. & Sahlberg, M. (2022). Magnetic and Structural Properties of the Fe5Si1-xGexB2 System. Journal of Solid State Chemistry, 316, Article ID 123576.
Open this publication in new window or tab >>Magnetic and Structural Properties of the Fe5Si1-xGexB2 System
Show others...
2022 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 316, article id 123576Article in journal (Refereed) Published
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.

National Category
Condensed Matter Physics
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-473290 (URN)10.1016/j.jssc.2022.123576 (DOI)000863761000008 ()
Funder
Swedish Foundation for Strategic Research, EM-16-0039Swedish Research Council, 2019-00207
Available from: 2022-04-25 Created: 2022-04-25 Last updated: 2022-10-28Bibliographically approved
Rosenqvist Larsen, S., Hedlund, D., Clulow, R., Sahlberg, M., Svedlindh, P., Delczeg-Czirjak, E. K. & Cedervall, J. (2022). Magnetism and magnetic structure determination of a selected (Mn,Co)(23)B-6-compound. Journal of Alloys and Compounds, 905, Article ID 164225.
Open this publication in new window or tab >>Magnetism and magnetic structure determination of a selected (Mn,Co)(23)B-6-compound
Show others...
2022 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 905, article id 164225Article in journal (Refereed) Published
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

Place, publisher, year, edition, pages
ElsevierElsevier BV, 2022
Keywords
Magnetism, X-ray diffraction, Neutron diffraction, First principles calculations
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-473658 (URN)10.1016/j.jallcom.2022.164225 (DOI)000779903700003 ()
Funder
Swedish Research CouncilSwedish Foundation for Strategic Research , EM-16-0 039StandUp
Available from: 2022-05-02 Created: 2022-05-02 Last updated: 2024-01-15Bibliographically approved
Hedlund, D. (2022). New and old materials for permanent magnets based on earth-abundant elements. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>New and old materials for permanent magnets based on earth-abundant elements
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Electrical motors, which find use in e.g. electrical vehicles, require per-manent magnets to function. Comparing ferrite magnets and Nd-based magnets reveals a large difference in their price and performance. During the last decade, gap-magnets, with performance in between ferrites and Nd-based magnets have attracted considerable research interest world-wide due to the “rare-earth crisis”. During this crisis, the price of certain rare-earth elements experienced volatile changes. This thesis deals with materials that could be relevant as gap-magnets. The thesis starts with introducing key properties and constraints relevant for gap-magnets. In the thesis, four different systems were investigated. The four systems show that permanent magnets need to be understood and optimized on three distinct levels, the crystal level, the structural level, and the micro-structural level. They show how old and new materials can potentially be utilized as permanent magnets. Lastly, the thesis ends with an outlook that presents new ideas for finding new permanent magnets. The ideas presented in the outlook are ideas that were not treated in this thesis, and thus may represent new ways for further work in developing materials for gap-magnets. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2022. p. 83
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2160
Keywords
permanent magnets, material development, sustainability
National Category
Condensed Matter Physics
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-473377 (URN)978-91-513-1525-6 (ISBN)
Public defence
2022-06-14, Polhelmssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2022-05-23 Created: 2022-04-26 Last updated: 2022-06-15
Larsen, S. R., Shtender, V., Hedlund, D., Delczeg-Czirjak, E. K., Beran, P., Cedervall, J., . . . Sahlberg, M. (2022). Revealing the Magnetic Structure and Properties of Mn(Co,Ge)2. Inorganic Chemistry, 61(44), 17673-17681
Open this publication in new window or tab >>Revealing the Magnetic Structure and Properties of Mn(Co,Ge)2
Show others...
2022 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 61, no 44, p. 17673-17681Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2022
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-473292 (URN)10.1021/acs.inorgchem.2c02758 (DOI)000877353500001 ()36270053 (PubMedID)
Funder
Swedish Foundation for Strategic Research, EM-16-0039eSSENCE - An eScience CollaborationSwedish National Infrastructure for Computing (SNIC), snic2021-1-36Swedish National Infrastructure for Computing (SNIC), snic2021-5-340Swedish Research Council, 2019-00645Knut and Alice Wallenberg Foundation
Available from: 2022-04-25 Created: 2022-04-25 Last updated: 2023-02-22Bibliographically approved
Breijaert, T. C., Daniel, G., Hedlund, D., Svedlindh, P., Kessler, V. G., Granberg, H., . . . Seisenbaeva, G. A. (2022). Self-assembly of ferria-nanocellulose composite fibres. Carbohydrate Polymers, 291, Article ID 119560.
Open this publication in new window or tab >>Self-assembly of ferria-nanocellulose composite fibres
Show others...
2022 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 291, article id 119560Article in journal (Refereed) Published
Abstract [en]

An environmentally benign synthesis of a magnetically responsive carboxymethylated cellulose nanofibril-based material is reported. Applied experimental conditions lead to the in-situ formation of magnetite nanoparticles with primary particle sizes of 2.0-4.0 nm or secondary particles of 3.6-16.4 nm depending on whether nucleation occurred between individual carboxymethylated cellulose nanofibrils, or on exposed fibril surfaces. The increase in magnetite particle size on the cellulose fibril surfaces was attributed to Ostwald ripening, while the small particles formed within the carboxymethyl cellulose aggregates were presumably due to steric interactions. The magnetite nanoparticles were capable of coordinating to carboxymethylated cellulose nanofibrils to form large "fibre-like" assemblies. The confinement of small particles within aggregates of reductive cellulose molecules was most likely responsible for excellent conservation of magnetic characteristics on storage of this material. The possibility for using the material in drug delivery applications with release rate controlled by daylight illumination is presented.

Place, publisher, year, edition, pages
ElsevierElsevier BV, 2022
Keywords
Nanocellulose, Magnetite, Magnetic composites, Hybrid materials, Photo-induced drug delivery
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:uu:diva-476801 (URN)10.1016/j.carbpol.2022.119560 (DOI)000799067800004 ()
Funder
Swedish Research CouncilThe Swedish Foundation for International Cooperation in Research and Higher Education (STINT)
Available from: 2022-06-20 Created: 2022-06-20 Last updated: 2024-01-15Bibliographically approved
Vishina, A., Hedlund, D., Shtender, V., Delczeg-Czirjak, E. K., Larsen, S. R., Vekilova, O. Y., . . . Herper, H. C. (2021). Data-driven design of a new class of rare-earth free permanent magnets. Acta Materialia, 212, Article ID 116913.
Open this publication in new window or tab >>Data-driven design of a new class of rare-earth free permanent magnets
Show others...
2021 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 212, article id 116913Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2021
Keywords
Permanent magnets, Rare-earth, Synthesis, DFT, Magnetism
National Category
Condensed Matter Physics Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-448912 (URN)10.1016/j.actamat.2021.116913 (DOI)000663657100005 ()
Funder
VinnovaSwedish Foundation for Strategic Research SweGRIDS - Swedish Centre for Smart Grids and Energy StorageSwedish Energy AgencySwedish Research CouncilKnut and Alice Wallenberg FoundationStandUpSwedish National Infrastructure for Computing (SNIC)
Available from: 2021-07-12 Created: 2021-07-12 Last updated: 2024-01-15Bibliographically approved
Shtender, V., Stopfel, H., Hedlund, D., Karlsson, D., Pothala, R., Skårman, B., . . . Sahlberg, M. (2021). Influence of nano-VC on the structural and magnetic properties of MnAlC-alloy. Scientific Reports, 11, Article ID 14453.
Open this publication in new window or tab >>Influence of nano-VC on the structural and magnetic properties of MnAlC-alloy
Show others...
2021 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 11, article id 14453Article in journal (Refereed) Published
Abstract [en]

Alloys of Mn55Al45C2 with additions of VC nano-particles have been synthesized and their properties evaluated. The Mn55Al45C2(VC)(x) (x=0.25, 0.5 and 1) alloys have been prepared by induction melting resulting in a high content of the ferromagnetic tau -phase (>94 wt.%). Powder X-ray diffraction indicates that nano-VC can be dissolved in the alloy matrix up to 1 at.%. On the other side, metallography investigations by scanning electron microscopy and scanning transmission electron microscope show inclusions of the nanosized additives in the microstructure. The effect of nano-VC on the grain and twin boundaries has been studied by electron backscattering diffraction. The magnetization has been measured by magnetometry up to 9 T while the domain structure has been studied using both magnetic force microscopy as well as Kerr-microscopy. For nano-VC contents above 0.25 at.%, a clear increase of the coercive force is observed, from 57 to 71 kA/m. The optimum appears to be for 0.5 at.% nano-VC which shows a 25% increase in coercive force without losing any saturation magnetization. This independent increase in coercivity is believed to originate from the nano-VC reducing the overall magnetic domain size. Overall, we observe that addition of nano-VC could be an interesting route to increase the coercive force of MnAl, without sacrificing saturation magnetization.

Place, publisher, year, edition, pages
Springer NatureNATURE RESEARCH, 2021
National Category
Condensed Matter Physics Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-452947 (URN)10.1038/s41598-021-93395-2 (DOI)000675633500020 ()34262064 (PubMedID)
Available from: 2021-09-13 Created: 2021-09-13 Last updated: 2024-01-15Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3574-2146

Search in DiVA

Show all publications