Bi-quadratic magnetoelectric coupling in underdoped La_2CuO_{4+x}

TL;DR

This paper investigates the bi-quadratic magnetoelectric coupling in lightly doped La_2CuO_{4+x} using a Ginzburg-Landau approach, exploring how magnetic fields influence electric polarization and the role of Dzyaloshinskii-Moriya interactions.

Contribution

It demonstrates how bi-quadratic free energy terms and Dzyaloshinskii-Moriya interactions explain the magnetoelectric effects in La_2CuO_{4+x}.

Findings

Magnetoelectric response can be explained by bi-quadratic interactions.

External magnetic fields influence electric polarization behavior.

Dzyaloshinskii-Moriya interaction plays a key role in generating the response.

Abstract

The recent discovery of relaxor ferroelectricity and magnetoelectric effect in lightly doped cuprate material La_2CuO_{4+x} has provided a number of questions concerning its theoretical description. It has been argued using a Ginzburg-Landau free energy approach that the magnetoelectric effect can be explained by the presence of bi-quadratic interaction terms in the free energy. Here, by using the same free energy functional, we study the variety of behavior which can emerge in the electric polarization under an external magnetic field. Subsequently, we discuss the role of Dzyaloshinskii-Moriya interaction in generating this magnetoelectric response. This work is particularly relevant for such relaxor systems where the material-dependent parameters would be affected by changes in e.g. chemical doping or cooling rate.