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Magnetic properties of the Fe5SiB2−Fe5PB2 system
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 Chemistry - Ångström, Inorganic Chemistry.ORCID iD: 0000-0003-0336-2560
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Materials Theory, ETH Zürich.ORCID iD: 0000-0002-3326-7786
Polish Academy of Sciences.
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2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, 094433Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Physical Society, 2017. Vol. 96, 094433
Keyword [sv]
Magnetism, Ferromagnetism, First-principle calculations, Magnetic interactions, Magnetic order parameter, Magnetic phase transition
National Category
Condensed Matter Physics Engineering and Technology
Research subject
Physics
Identifiers
URN: urn:nbn:se:uu:diva-330463DOI: 10.1103/PhysRevB.96.094433OAI: oai:DiVA.org:uu-330463DiVA: diva2:1145561
Available from: 2017-09-29 Created: 2017-09-29 Last updated: 2017-10-20Bibliographically approved
In thesis
1. Magnetic Materials for Cool Applications: Relations between Structure and Magnetism in Rare Earth Free Alloys
Open this publication in new window or tab >>Magnetic Materials for Cool Applications: Relations between Structure and Magnetism in Rare Earth Free Alloys
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

New and more efficient magnetic materials for energy applications are a big necessity for sustainable future. Whether the application is energy conversion or refrigeration, materials based on sustainable elements should be used, which discards all rare earth elements. For energy conversion, permanent magnets with high magnetisation and working temperature are needed whereas for refrigeration, the entropy difference between the non-magnetised and magnetised states should be large. For this reason, magnetic materials have been synthesised with high temperature methods and structurally and magnetically characterised with the aim of making a material with potential for large scale applications. To really determine the cause of the physical properties the connections between structure (crystalline and magnetic) and, mainly, the magnetic properties have been studied thoroughly.

The materials that have been studied have all been iron based and exhibit properties with potential for the applications in mind. The first system, for permanent magnet applications, was Fe5SiB2. It was found to be unsuitable for a permanent magnet, however, an interesting magnetic behaviour was studied at low temperatures. The magnetic behaviour arose from a change in the magnetic structure which was solved by using neutron diffraction. Substitutions with phosphorus (Fe5Si1-xPxB2) and cobalt (Fe1-xCox)5PB2 were then performed to improve the permanent magnet potential. While the permanent magnetic potential was not improved with cobalt substitutions the magnetic transition temperature could be greatly controlled, a real benefit for magnetic refrigeration. For this purpose AlFe2B2 was also studied, and there it was found, conclusively, that the material undergoes a second order transition, making it unsuitable for magnetic cooling. However, the magnetic structure was solved with two different methods and was found to be ferromagnetic with all magnetic moments aligned along the crystallographic a-direction. Lastly, the origin of magnetic cooling was studied in Fe2P, and can be linked to the interactions between the magnetic and atomic vibrations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 70 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1585
Keyword
Magnetism, Diffraction, X-ray scattering, Neutron Scattering, Permanent magnets, Magnetocalorics
National Category
Organic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-331762 (URN)978-91-513-0123-5 (ISBN)
Public defence
2017-12-08, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
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Supervisors
Available from: 2017-11-16 Created: 2017-10-20 Last updated: 2017-11-16

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Publisher's full texthttps://journals.aps.org/prb/abstract/10.1103/PhysRevB.96.094433

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Hedlund, DanielCedervall, JohanEdström, AlexanderKontos, SofiaEriksson, OlleRusz, JanSvedlindh, PeterSahlberg, MartinGunnarsson, Klas

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