Berlin 2018 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 8: Multiferroics and magnetoelectrics I (joint session MA/KFM)

KFM 8.8: Vortrag

Dienstag, 13. März 2018, 11:30–11:45, EB 202

Magnetic and Polar Properties of the Lacunar Spinel GaMo₄S₈ — •Korbinian Geirhos¹, Peter Lunkenheimer¹, Hiroyuki Nakamura², Yoshikazu Tabata², and István Kézsmárki¹ — ¹Experimental Physics V, EKM, University of Augsburg, Germany — ²Department of Materials Science and Engineering, Kyoto University, Japan

The compound GaMo₄S₈ belongs to the family of lacunar spinels AM₄X₈ (A=Ga and Ge; M=V, Mo, Nb, and Ta; X= S and Se). Many of these lacunar spinels exhibit a Jahn-Teller transition associated with ferroorbital ordering. In the so far investigated compounds GaV₄S₈, GaV₄Se₈ and GeV₄S₈, the onset of orbital-order induced ferroelectricity was found at the Jahn-Teller transition [1,2,3]. Moreover, all of these three materials show strong magnetoelectric coupling with distinct values of the polarization in their magnetically ordered phases, including a skyrmion lattice state, as shown for GaV₄S₈ and GaV₄Se₈ [1, 4]. It was proposed that these skyrmions, which are topologically protected spin textures, carry additional electric polarization [1]. We extend these investigations to another lacunar spinel, GaMo₄S₈. The polar properties of this compound were studied by dielectric spectroscopy and pyrocurrent measurements. It shows a Jahn-Teller transition at 47 K, again accompanied by polar ordering. In addition, below 20 K GaMo₄S₈ exhibits a complex magnetic phase diagram.
E. Ruff et al., Sci. Adv. 1, E1500916 (2015). [2] E. Ruff et al., Phys. Rev. B 96, 165119 (2017). [3] K. Singh et al., Phys. Rev. Lett. 113, 137602 (2014). [4] Y. Fujima et al., Phys. Rev. B 95, 180410 (2017)