Theory of the magnetoeletric effect in a lightly doped high-Tc cuprate

TL;DR

This paper develops a Landau theory to explain the magnetoelectric effects in underdoped La_2CuO_(4+x), revealing anisotropic responses, feedback effects on magnetization, and predicting a magnetocapacitive phenomenon.

Contribution

It introduces a bi-quadratic magnetoelectric coupling model that explains experimental observations and predicts new low-temperature effects in lightly doped high-Tc cuprates.

Findings

Bi-quadratic coupling explains polarization dependence on magnetic field.

Feedback enhancement of magnetization occurs below ferroelectric transition.

Prediction of a magnetocapacitive effect in the material.

Abstract

In a recent study Viskadourakis et al. discovered that extremely underdoped La_2CuO_(4+x) is a relaxor ferroelectric and a magnetoelectric material at low temperatures. It is further observed that the magnetoelectric response is anisotropic for different directions of electric polarization and applied magnetic field. By constructing an appropriate Landau theory, we show that a bi-quadratic magnetoelectric coupling can explain the experimentally observed polarization dependence on magnetic field. This coupling leads to several novel low-temperature effects including a feedback enhancement of the magnetization below the ferroelectric transition, and a predicted magnetocapacitive effect.