Dresden 2017 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 10: Caloric Effects in Ferromagnetic Materials
MA 10.1: Hauptvortrag
Montag, 20. März 2017, 15:00–15:30, HSZ 04
Magnetoelastic coupling and lattice dynamics in magnetocaloric materials — •Markus Ernst Gruner1, Werner Keune1, Michael Wolloch2, Peter Mohn2, Oliver Gutfleisch3, Heiko Wende1, and Rossitza Pentcheva1 — 1University of Duisburg-Essen — 2TU Vienna — 3TU Darmstadt
Solid state cooling concepts based on
magnetocaloric materials offer an energy-efficient
alternative to the conventional gas-compressor scheme.
Large magnetocaloric effects are observed near magnetic first order
transitions which involve a simultaneous change in volume or lattice symmetry
and are subject to hysteresis losses.
In metamagnetic Heusler alloys, lattice vibrations and
magnetic order provide competing contributions to the entropy change,
which further reduces the performance [1].
In metamagnetic FeRh [2] and conventional magnetocaloric
La-Fe-Si-based compounds [3],
lattice and magnetic degrees of freedom contribute cooperatively
to the free energy.
Comparing recent results from first-principles calculations and
nuclear resonant inelastic X-ray scattering, we will review the relevant mechanisms
for the favorable coupling of magnetism and lattice degrees of freedom in these
two systems and discuss strategies to reduce the intrisic causes of hysteresis.
Contributions from researchers of Argonne National Laboratory,
the universities of Bochum, Darmstadt, Duisburg-Essen and Vienna, IFW Dresden, KIT
and the SPP 1599 are gratefully acknowledged.
[1] T. Gottschall et al., Phys. Rev. B 93, 184431(2016)
[2] M. Wolloch et al., Phys. Rev. B 94, 174435 (2016)
[3] M. E. Gruner et al.
Phys. Rev. Lett. 114, 057202 (2015)