Switching the Ferroelectric Polarization by External Magnetic Fields in the Spin = 1/2 Chain Cuprate LiCuVO4

TL;DR

This study investigates how external magnetic fields can switch ferroelectric polarization in the multiferroic LiCuVO4 by reorienting its spiral spin order, revealing strong magnetoelectric coupling and a detailed phase diagram.

Contribution

It provides the first detailed experimental analysis of magnetic field-induced polarization switching and phase transitions in LiCuVO4, confirming theoretical symmetry predictions.

Findings

Polarization can be switched by magnetic field reorientation of the spiral spin order.

Above 7.5 T, the material becomes collinear and paraelectric.

The phase diagram shows strong coupling between magnetic and ferroelectric phases.

Abstract

We present a detailed study of complex dielectric constant and ferroelectric polarization in multiferroic LiCuVO4 as function of temperature and external magnetic field. In zero external magnetic field, spiral spin order with an ab helix and a propagation vector along the crystallographic b direction is established, which induces ferroelectric order with spontaneous polarization parallel to a. The direction of the helix can be reoriented by an external magnetic field and allows switching of the spontaneous polarization. We find a strong dependence of the absolute value of the polarization for different orientations of the spiral plane. Above 7.5 T, LiCuVO4 reveals collinear spin order and remains paraelectric for all field directions. Thus this system is ideally suited to check the symmetry relations for spiral magnets as predicted theoretically. The strong coupling of ferroelectric and magnetic order is documented and the complex (B,T) phase diagram is fully explored.