First-order ferromagnetic transitions of lanthanide local moments in divalent compounds: An itinerant electron positive feedback mechanism and Fermi surface topological change

Around discontinuous (first-order) magnetic phase transitions, the strong caloric response of materials to the application of small fields is widely studied for the development of solid-state refrigeration. Typically strong magnetostructural coupling drives such transitions and the attendant substan...

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Bibliographic Details
Published in:Physical review. B 2020-05, Vol.101 (17), p.1, Article 174437
Main Authors: Mendive-Tapia, Eduardo, Paudyal, Durga, Petit, Leon, Staunton, Julie B.
Format: Article
Language:English
Subjects:
Fermi surfaces
Ferromagnetism
Magnetism
Phase transitions
Positive feedback
Refrigeration
Topology
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Summary:Around discontinuous (first-order) magnetic phase transitions, the strong caloric response of materials to the application of small fields is widely studied for the development of solid-state refrigeration. Typically strong magnetostructural coupling drives such transitions and the attendant substantial hysteresis dramatically reduces the cooling performance. In this context, we describe a purely electronic mechanism which pilots a first-order paramagnetic-ferromagnetic transition in divalent lanthanide compounds and which explains the giant nonhysteretic magnetocaloric effect recently discovered in a Eu2In compound. There is a positive feedback between the magnetism of itinerant valence electrons and the ferromagnetic ordering of local f-electron moments, which appears as a topological change to the Fermi surface. The origin of this electronic mechanism stems directly from Eu's divalency, which explains the absence of a similar discontinuous transition in Gd2In.
ISSN:2469-9950
2469-9969
DOI:10.1103/PhysRevB.101.174437