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Data-driven design of a new class of rare-earth free permanent magnets
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.ORCID iD: 0000-0002-4583-2877
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.ORCID iD: 0000-0003-3574-2146
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.ORCID iD: 0000-0002-8690-9957
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
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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. Vol. 212, article id 116913
Keywords [en]
Permanent magnets, Rare-earth, Synthesis, DFT, Magnetism
National Category
Condensed Matter Physics Materials Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-448912DOI: 10.1016/j.actamat.2021.116913ISI: 000663657100005OAI: oai:DiVA.org:uu-448912DiVA, id: diva2:1580000
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
In thesis
1. New and old materials for permanent magnets based on earth-abundant elements
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
2. Strategies for finding new magnetic materials
Open this publication in new window or tab >>Strategies for finding new magnetic materials
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Magnetic materials are indispensable in modern day society. The vast majority of energy generation and conversion involves some kind of magnetic material, and several other applications such as data storage also use them. Despite this there are relatively few types of magnetic materials in use today, which is due to the difficulty of finding new materials that have the necessary properties. In this thesis synthesis of new magnetic materials is performed using a variety oftechniques in an attempt to identify a structured approach to finding crystal structures suited for further development.

Three approaches for developing new magnetic materials were used. Targeted substitutions of Mn was done in AlCoCrFeMnxNi and Mn3Co20B6, where Mn provided significant contributions to the magnetic moment, at the cost of stability of the ferromagnetic structures. A new system was identified using theoretical screening, Mn2Co3Ge, which was successfully synthesised. Application of the substitution method revealed properties in the system favourable for magnetic refrigeration. New systems were also discovered in synthesis attempts of Mn2Co3Ge and Ce-based magnets, but these materials were ferrimagnetic, or canted anti-ferromagnetic, resulting in low magnetisation.

Varying degrees of success were seen in creating magnetic materials with these approaches. Theoretical screening is likely to become an incredibly powerful tool in the future as more understanding of systems is gained. Complementing the theoretical screening method with the newly discovered structures could be a promising avenue for developing new applicable materials. Substitution of elements will remain an extremely powerful tool for tuning properties and by combining it with theoretical screening will likely be key to discovering new applicable magnet systems in the future.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2022. p. 59
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2198
Keywords
Magnetic materials, Materials development, Alloys
National Category
Materials Chemistry
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-486285 (URN)978-91-513-1617-8 (ISBN)
Public defence
2022-11-24, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2022-11-02 Created: 2022-10-06 Last updated: 2022-11-02

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Vishina, AlenaHedlund, DanielShtender, VitaliiDelczeg-Czirjak, Erna K.Larsen, Simon R.Vekilova, Olga Yu.Huang, ShuoVitos, LeventeSvedlindh, PeterSahlberg, MartinEriksson, OlleHerper, Heike C.

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Vishina, AlenaHedlund, DanielShtender, VitaliiDelczeg-Czirjak, Erna K.Larsen, Simon R.Vekilova, Olga Yu.Huang, ShuoVitos, LeventeSvedlindh, PeterSahlberg, MartinEriksson, OlleHerper, Heike C.
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