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MA: Fachverband Magnetismus

MA 24: Magnetic Materials I

MA 24.3: Vortrag

Mittwoch, 18. März 2015, 10:00–10:15, H 0112

Element-resolved thermodynamics of LaFe_13−xSi_x — •Markus Ernst Gruner^1,2,3, Werner Keune^2,4, Beatriz Roldan Cuenya⁵, Claudia Weis², Joachim Landers², Sergey I. Makarov², David Klar², Michael Y. Hu⁶, Ercan E. Alp⁶, Jiyong Zhao⁶, Maria Krautz¹, Oliver Gutfleisch⁷, and Heiko Wende² — ¹IFW Dresden — ²Universität Duisburg-Essen — ³Forschungs-Neutronenquelle FRM II, Garching — ⁴MPI Halle — ⁵Ruhr-Universität Bochum — ⁶Argonne National Laboratory — ⁷TU Darmstadt

By combination of two independent approaches, nuclear resonant inelastic X-ray scattering and first-principles calculations in the framework of density functional theory, we demonstrate an unusual and significant effect of the magnetic phase transition on the element-resolved vibrational density of states of LaFe_13−xSi_x. This comprises the disapperance of a high-energy peak in connection with an overall softening of phonons in the paramagnetic phase, which is unexpected due to the large volume decrease at the transition. The pronounced magnetoelastic effect originates from adiabatic electron phonon coupling caused by specific changes in the electronic density of states at the Fermi level arising from the itinerant electron metamagnetism of Fe. The increase in lattice entropy associated with the Fe subsystem is significant and contributes cooperatively with the magnetic and electronic entropy changes to the excellent magneto- and barocaloric properties.