Orbital-Order Driven Ferroelectricity and Dipolar Relaxation Dynamics in Multiferroic GaMo${}_4$S${}_8$

Abstract

We present the results of broadband dielectric spectroscopy of GaMo${}_4$S${}_8$, a lacunar spinel system that recently was shown to exhibit non-canonical, orbitally-driven ferroelectricity. Our study reveals complex relaxation dynamics of this multiferroic material, both above and below its Jahn-Teller transition at T${}_{\text{JT}}=47$ K. Above T${}_{\text{JT}}$, two types of coupled dipolar-orbital dynamics seem to compete: relaxations within cluster-like regions with short-range polar order like in relaxor ferroelectrics and critical fluctuations of only weakly interacting dipoles, the latter resembling the typical dynamics of order-disorder type ferroelectrics. Below the Jahn-Teller transition, the onset of orbital order drives the system into long-range ferroelectric order and dipolar dynamics within the ferroelectric domains is observed. The coupled dipolar and orbital relaxation behavior of GaMo${}_4$S${}_8$ above the Jahn-Teller transition markedly differs from that of the skyrmion host GaV${}_4$S${}_8$, which seems to be linked to differences in the structural distortions of the two systems on the unit-cell level.

arXiv comment6 pages, 3 figures + Supplemental Material (2 pages, 2 figures)

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Cited by in corpus (7)

• Macroscopic Manifestation of Domain-wall Magnetism and Magnetoelectric Effect in a Néel-type Skyrmion Host
• Cooperative cluster-Jahn-Teller effect as a possible route to antiferroelectricity
• Lattice dynamics and electronic excitations in a large family of lacunar spinels with a breathing pyrochlore lattice structure
• Antipolar transitions in GaNb${}_4$Se${}_8$ and GaTa${}_4$Se${}_8$
• Novel $J_{\mathrm{eff}}$=3/2 Metallic Phase and Unconventional Superconductivity in GaTa${}_4$Se${}_8$
• Spin dynamics in the skyrmion-host lacunar spinel GaV4S8
• Optical, dielectric, and magnetoelectric properties of ferroelectric and antiferroelectric lacunar spinels