Multiferroicity and colossal magneto-capacitance in Cr-thiospinels

TL;DR

This paper reviews the magnetic and dielectric properties of Cr-thiospinels RCr2S4 (R=Cd, Hg), highlighting their multiferroic behavior and colossal magneto-capacitance driven by relaxation dynamics near magnetic transitions.

Contribution

It provides a comprehensive investigation of the magnetic and dielectric properties of RCr2S4 compounds, revealing their multiferroic nature and colossal magneto-capacitive effects.

Findings

Colossal magneto-capacitive effect observed at magnetic transition.

Ferromagnetic and ferroelectric coexistence in Cr-thiospinels.

Magnetocapacitive coupling driven by relaxation dynamics.

Abstract

The sulfur based Cr-spinels RCr2S4 with R = Cd and Hg exhibit the coexistence of ferromagnetic and ferroelectric properties together with a pronounced magnetocapacitive coupling. While in CdCr2S4 purely ferromagnetic order is established, in HgCr2S4 a bond-frustrated magnetic ground state is realized, which, however, easily can be driven towards a ferromagnetic configuration in weak magnetic fields. This paper shall review our recent investigation for both compounds. Besides the characterization of the magnetic properties, the complex dielectric permittivity was studied by means of broadband dielectric spectroscopy as well as measurements of polarization hysteresis and pyro-currents. The observed colossal magneto-capacitive effect at the magnetic transition seems to be driven by an enormous variation of the relaxation dynamics.