Multiferroicity due to nonstoichiometry in the chain cuprate LiVCuO_4

TL;DR

This paper explains the multiferroic behavior in LiVCuO_4 by considering exchange-induced electric polarization on Cu^2+ centers caused by nonstoichiometry, providing a new perspective beyond existing theories.

Contribution

It introduces a novel explanation for multiferroicity in LiVCuO_4 involving nonstoichiometric Cu^2+ centers, challenging previous models.

Findings

Exchange-induced electric polarization explains multiferroicity.

Cu^2+ centers serve as probes for spin incommensurability.

The model aligns with experimental observations.

Abstract

The recently observed multiferroic behavior in the s=1/2 chain cuprate LiVCuO_4 (LiCuVO_4) with edge-shared CuO_4 plaquettes and helical spin ordering does not agree with the existing theories such as a spin-current scenario. We argue that the effect can be consistently explained, if the exchange-induced electric polarization on the out-of-chain Cu^2+ centers substituting for Li-ions in LiVCuO_4 is taken into account. These substituent centers are proved to be an effective probe of the spin incommensurability and the magnetic field effects.