Magnetoelectric effect and phase transitions in CuO in external magnetic fields

TL;DR

This study reveals that high magnetic fields can control the electric polarization and magnetic phases in CuO, uncovering hidden magnetoelectric effects in this high-temperature multiferroic material.

Contribution

It demonstrates the magnetic field-induced suppression of spin modulation and electric polarization in CuO, revealing new magnetoelectric phenomena in a high-temperature multiferroic.

Findings

High magnetic fields suppress spin helical modulation in CuO.

Magnetic fields induce and then suppress incommensurate magnetic structures.

CuO exhibits hidden magnetoelectric effects at high fields.

Abstract

Apart from being so far the only known binary multiferroic compound, CuO has a much higher transition temperature into the multiferroic state, 230 K, than any other known material in which the electric polarization is induced by spontaneous magnetic order, typically lower than 100 K. Although the magnetically induced ferroelectricity of CuO is firmly established, no magnetoelectric effect has been observed so far as direct crosstalk between bulk magnetization and electric polarization counterparts. Here we demonstrate that high magnetic fields of about 50 T are able to suppress the helical modulation of the spins in the multiferroic phase and dramatically affect the electric polarization. Furthermore, just below the spontaneous transition from commensurate (paraelectric) to incommensurate (ferroelectric) structures at 213 K, even modest magnetic fields induce a transition into the incommensurate structure and then suppress it at higher field. Thus, remarkable hidden magnetoelectric features are uncovered, establishing CuO as prototype multiferroic with abundance of competitive magnetic interactions.