Magnetically-induced electric polarization in an organo-metallic magnet

TL;DR

This study demonstrates magnetically-induced electric polarization in an organo-metallic quantum magnet, revealing potential for designing multiferroics with large organic molecules and showing a quantum phase transition with coupled magnetic and electric order.

Contribution

It provides the first evidence of magnetoelectric effects in an organo-metallic material, expanding the scope of multiferroic research beyond oxides.

Findings

Electric polarization arises from non-collinear magnetic order.

Polarization can be switched hysteretically.

A magnetoelectric quantum phase transition occurs at low temperatures.

Abstract

The coupling between magnetic order and ferroelectricity has been under intense investigation in a wide range of transition-metal oxides. The strongest coupling is obtained in so-called magnetically-induced multiferroics where ferroelectricity arises directly from magnetic order that breaks inversion symmetry. However, it has been difficult to find non-oxide based materials in which these effects occur. Here we present a study of copper dimethyl sulfoxide dichloride (CDC), an organo-metallic quantum magnet containing $S = 1/2$ Cu spins, in which electric polarization arises from non-collinear magnetic order. We show that the electric polarization can be switched in a stunning hysteretic fashion. Because the magnetic order in CDC is mediated by large organic molecules, our study shows that magnetoelectric interactions can exist in this important class of materials, opening the road to designing magnetoelectrics and multiferroics using large molecules as building blocks. Further, we demonstrate that CDC undergoes a magnetoelectric quantum phase transition where both ferroelectric and magnetic order emerge simultaneously as a function of magnetic field at very low temperatures.