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MA: Fachverband Magnetismus
MA 61: Caloric Effects
MA 61.8: Vortrag
Freitag, 20. März 2020, 11:15–11:30, HSZ 101
Non-hysteretic first-order ferromagnetic transitions by itinerant electron feedback and Fermi surface topology change — •Eduardo Mendive Tapia1,2, Durga Paudyal3, Leon Petit4, and Julie Staunton2 — 1Max-Planck Institut für Eisenforschung, Düsseldorf, Germany — 2Dept of Physics, University of Warwick, Coventry, UK — 3The Ames Laboratory, U.S. Dept of Energy, Iowa State University, USA — 4Daresbury Laboratory, Warrington, UK
Refrigeration and air conditioning are crucial in modern life and in adapting to climate change. Discontinuous magnetic phase transitions have great promise for new, energy efficient and environmentally friendly solid-state cooling technology. Huge exploitable entropy and temperature changes typically result from the coupling between a material’s spin polarized interacting electrons and the crystal structure. Such magnetostructurally driven cooling, however, is nearly always degraded by hysteresis. We present an ab-initio theory which can find mechanisms for first-order magnetic phase transitions that are purely electronic in origin [1], thus avoiding the need for magnetostructural effects. We show that this electronic mechanism arises from an itinerant electron feedback to magnetic order. In particular, it is demonstrated that a topological change of the Fermi surface explains the hysteresis-free giant cooling properties recently measured in Eu2In [2].—This work is funded by the EPSRC (UK) and the U.S. Dept of Energy, and forms part of the PRETAMAG project (University of Warwick).
[1] E Mendive-Tapia and J Staunton, Phys. Rev. B 99, 144424 (2019)
[2] F Guillou et al., Nat. Comm. 9, 2925 (2018)