Regensburg 2016 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 20: Topical session: Caloric Effects in ferroic materials I - Magnetocalorics
MM 20.2: Vortrag
Dienstag, 8. März 2016, 10:45–11:00, H53
Element-resolved vibrational dynamics and thermodynamics of magnetocaloric FeRh compound — •Werner Keune1, Markus E. Gruner1, Joachim Landers1, Soma Salamon1, Franziska Scheibel1, Detlef Spoddig1, Beatriz Roldan Cuenya2, Oliver Gutfleisch3, Michael Y. Hu4, Jiyong Zhao4, Thomas Toellner4, Ercan E. Alp4, and Heiko Wende1 — 1Universität Duisburg-Essen, Germany — 2Ruhr-Universität Bochum, Germany — 3TU Darmstadt, Germany — 4Argonne National Laboratory, USA
Employing both 57Fe nuclear resonant inelastic X-ray scattering and first principles calculations (DFT), similar to ref. [1], we determined the Fe-projected phonon DOS of the B2-ordered magnetocaloric FeRh compound at temperatures below and above the first-order magneto-structural phase transition from the antiferromagnetic (AFM) to the ferromagnetic (FM) state. Two experimental 57FeRh(001) thin-film samples on MgO(001) with different stoichiometries (AFM and FM, respectively) were studied. Distinct differences between the phonon DOS of the AFM and FM states were found. However, this leads only to very small differences in the T-dependences of the Fe-projected vibrational (lattice) specific heat C(T) and the vibrational entropy S(T), respectively, for the two magnetic states. The experimental Debye-Waller factor indicates that the lattice of the AFM state is softer than in the FM state.
[1] M. E. Gruner et al., Phys. Rev. Lett. 114, 057202 (2015).