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Giant magnetocaloric effect in the (Mn,Fe)NiSi-system
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.ORCID iD: 0000-0003-2790-116x
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.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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2023 (English)Manuscript (preprint) (Other academic)
Abstract [en]

The search for energy-efficient and environmentally friendly cooling technologies is a key driver for the development of magnetic refrigeration based on the magnetocaloric effect (MCE). This phenomenon arises from the interplay between magnetic and lattice degrees of freedom that is strong in certain materials, leading to a change in temperature upon application or removal of a magnetic field. Here we report on a new material, Mn1−xFexNiSi0.95Al0.05, with an exceptionally large isothermal entropy at room temperature. By combining experimental and theoretical methods we outline the microscopic mechanism behind the large MCE in this material. It is demonstrated that the competition between the Ni2In-type hexagonal phase and the MnNiSi-type orthorhombic phase, that coexist in this system, combined with the distinctly different magnetic properties of these phases, is a key parameter for the functionality of this material for magnetic cooling.

Place, publisher, year, edition, pages
2023.
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-525213DOI: 10.48550/arXiv.2307.00128OAI: oai:DiVA.org:uu-525213DiVA, id: diva2:1845558
Available from: 2024-03-19 Created: 2024-03-19 Last updated: 2024-03-19
In thesis
1. Exploring magnetocaloric materials by ab-initio methods
Open this publication in new window or tab >>Exploring magnetocaloric materials by ab-initio methods
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis explores the characterization of magnetocaloric materials from first-principles calculations, emphasizing entropy variation associated with the magnetocaloric effect. The study happens in the context of the search for new magnetocaloric materials to be applied in domestic magnetic refrigerators,  as environmentally friendly and energy-efficient alternatives to conventional vapor-compression devices.

The study involves benchmarking entropy calculations in systems like FeRh, which exhibits a first-order metamagnetic transition, and Gd, with a second-order ferromagnetic-paramagnetic transition. Different levels of approximations are examined and compared against experimental data, highlighting the need to distinguish between first-order and second-order transitions in the approach taken. The tests underscore the necessity of calculating vibrational and elastic properties for both phases to accurately calculate the entropy variation. This insight is applied in the study of Mn0.5Fe0.5NiSi0.9Al0.05, with results consistent with experimental data.

Furthermore, the relationship between structural changes and magnetic properties is investigated, in particular for pressure-induced polymorphs in Gd and the phase transition in Mn0.5Fe0.5NiSi0.95Al0.05. In the case of Gd, it was shown that variations in magnetic ordering temperature under pressure could be explained through a model based on the formation and accumulation of stacking faults. For the Mn0.5Fe0.5NiSi0.95Al0.05 system, the adoption of a magnetic composite model, in conjunction with experimental data, allowed to determine that the magnetostructural transition in these compounds is predominantly driven by the lattice subsystem. 

The results positively confirm the feasibility of using first-principles entropy estimates as an effective screening tool in high-throughput studies for magnetocaloric materials. A promising workflow is proposed, demonstrating potential in its initial results. Through comparison with experimental data, the derived routes offer valuable insights for the further refinement of the workflow. This approach aims to enhance accuracy and systematically manage complex systems, highlighting a path forward for future advancements.

Lastly, the introduction of a novel scaling scheme in Monte Carlo simulations enhancing accuracy across various temperatures, represents a potential advancement in the field of magnetic simulations.

Place, publisher, year, edition, pages
Åbo, Finland: Åbo Akademi University, 2024
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2384
Keywords
magnetocaloric, magnetism, ab-initio
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-525219 (URN)978-952-12-4376-9 (ISBN)978-952-12-4377-6 (ISBN)
Public defence
2024-04-26, Häggsalen, Lägerhyddsvägen 1, 752 37 Uppsala, Uppsala, 09:00 (English)
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Available from: 2024-04-05 Created: 2024-03-19 Last updated: 2024-04-05

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Ghorai, SagarVieira, Rafael MartinhoShtender, VitaliiDelczeg-Czirjak, Erna KrisztinaHerper, Heike C.Simak, Sergei I.Eriksson, OlleSahlberg, MartinSvedlindh, Peter

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Ghorai, SagarVieira, Rafael MartinhoShtender, VitaliiDelczeg-Czirjak, Erna KrisztinaHerper, Heike C.Simak, Sergei I.Eriksson, OlleSahlberg, MartinSvedlindh, Peter
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Solid State PhysicsMaterials TheoryInorganic ChemistryApplied Material ScienceInorganic ChemistryTheoretical MagnetismExperimental PhysicsAnalytical ChemistrySolid State PhysicsPhysics IPhysics IVCondensed Matter TheoryMaterials TheoryDepartment of Physics and AstronomyPhysics IIIPhysics VMaterials PhysicsStructural ChemistrySurface BiotechnologyDepartment of Materials ScienceMaterials Science
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