Regensburg 2019 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 7: Multiferroics

KFM 7.5: Vortrag

Montag, 1. April 2019, 16:20–16:40, H47

Orbital-Order Driven Ferroelectricity and Dipolar Relaxation Dynamics in Multiferroic GaMo₄S₈ — •Korbinian Geirhos¹, Peter Lunkenheimer¹, Hiroyuki Nakamura², Takeshi Waki², Yoshikazu Tabata², and Istvan Kezsmarki¹ — ¹Experimental Physics V, EKM, University of Augsburg — ²Department of Materials Science and Engineering, Kyoto University, Japan

GaMo₄S₈, a compound of the lacunar spinel family, was recently shown to exhibit non-canonical, orbitally-driven ferroelectricity [1]. Our dielectric spectroscopy measurements on this multiferroic material reveal complex relaxation dynamics, above as well as below its Jahn-Teller transition at T_JT = 47 K [2]. Above the Jahn-Teller transition, two types of coupled dipolar-orbital dynamics were found: On the one hand, relaxations within cluster-like regions with short-range polar order, as known from relaxor ferroelectrics. On the other hand, critical fluctuations of only weakly interacting dipoles, resembling the typical dynamics of order-disorder type ferroelectrics. Below T_JT, the system is driven into long range ferrolectric order by the onset of orbital order and dipolar dynamics within the ferroelectric domains is observed: The found marked differences to the skyrmion host GaV₄S₈, seem to be related to the different structural distortions in these systems.

[1] E. Neuber,et al., J. Phys.: Condens. Matter 30, 445402 (2018) [2] K. Geirhos, et al., arXiv:1810.07145