Ferroelectric Transition Induced by the Incommensurate Magnetic Ordering in LiCuVO4

TL;DR

This paper reports the discovery of a ferroelectric transition in LiCuVO4 that coincides with helical magnetic ordering, linked to incommensurate magnetic structure and influenced by magnetic fields.

Contribution

It demonstrates the direct correlation between incommensurate magnetic order and ferroelectricity in LiCuVO4, providing experimental evidence for the predicted relation between polarization and magnetic structure.

Findings

Ferroelectric transition occurs with helical spin order in LiCuVO4.

Electric polarization is proportional to the product of the incommensurate wave vector and helical axis.

Transition temperature decreases under applied magnetic field.

Abstract

A ferroelectric transition occurring simultaneously with helical spin order has been found in both the polycrystalline and single crystal samples of LiCuVO4. The system has Cu2+ spins (s=1/2) of the CuO2 chains formed of edge-sharing CuO4 squares. Possibly due to the frustrated nature caused by the competition between the nearest-neighbor and next-nearest-neighbor exchange interactions, Cu spins exhibit, as has been already reported, the helical magnetic order with the incommensurate modulation vector Q along the chain direction and with the helical axis e3 perpendicular to the CuO4 squares. The electric polarization P can be understood by the recently predicted relation (P is proportional to Q*e3). The transition temperature has been found to be gradually suppressed by the applied magnetic field.