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Revealing the Magnetic Structure and Properties of Mn(Co,Ge)2
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.ORCID iD: 0000-0002-8107-4110
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, Technology, Department of Materials Science and Engineering, Solid State Physics.ORCID iD: 0000-0003-3574-2146
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
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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. Vol. 61, no 44, p. 17673-17681
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-473292DOI: 10.1021/acs.inorgchem.2c02758ISI: 000877353500001PubMedID: 36270053OAI: oai:DiVA.org:uu-473292DiVA, id: diva2:1653823
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 FoundationAvailable from: 2022-04-25 Created: 2022-04-25 Last updated: 2023-02-22Bibliographically 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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Larsen, Simon R.Shtender, VitaliiHedlund, DanielDelczeg-Czirjak, Erna K.Vishina, AlenaHerper, Heike C.Svedlindh, PeterEriksson, OlleSahlberg, Martin

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Larsen, Simon R.Shtender, VitaliiHedlund, DanielDelczeg-Czirjak, Erna K.Vishina, AlenaHerper, Heike C.Svedlindh, PeterEriksson, OlleSahlberg, Martin
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