Dresden 2017 – wissenschaftliches Programm
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TUT: Tutorien
TUT 1: Tutorial: Ferroics and Skyrmions
TUT 1.2: Tutorium
Sonntag, 19. März 2017, 16:50–17:40, HSZ 304
Skyrmions with ferroelectric polarization in multiferroic lacunar spinels — •Alois Loidl — Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Germany
This tutorial will provide an introductory discussion of polar properties induced by topological spin order. Lacunar spinels will be taken as illuminating examples. They undergo orbital ordering and at low temperatures reveal complex magnetic phases. GaV4S8 and GaV4Se8 show ferromagnetic, cycloidal and Néel-type skyrmion lattice phases [1,2]. We provide a thorough study of the polar properties and show that the orbitally ordered phases are ferroelectric [3]. Moreover, spin-driven excess polarizations emerge in all magnetic phases. Hence, they host a zoo of multiferroic phases including the skyrmion lattice of spin vortices dressed with ferroelectric polarization [3]. The low-temperature magnetic phase diagrams document the importance of anisotropy: GaV4S8 is an easy axis magnet with a narrow skyrmion-lattice pocket only. In clear distinction, GaV4Se8 is governed by easy plane anisotropy, its skyrmion phase is drastically extended and reaches from the magnetic phase boundary down to the lowest temperatures.
[1] I. Kézsmárki et al., Nature Materials 14, 1116 (2015).
[2] S. Widmann et al., Phil. Mag. (2016), in press.
[3] E. Ruff et al., Science Advances 1, E1500916 (2015).