The effect of transverse magnetic correlations on a coupled order parameter: shifted transition temperatures and thermal hysteresis

TL;DR

This paper investigates how transverse magnetic correlations influence electric polarization in multiferroic materials, revealing effects like shifted transition temperatures and thermal hysteresis due to magnetic fluctuations.

Contribution

It introduces a Green's function approach with RPA to analyze the impact of magnetic correlations on coupled electric and magnetic order parameters.

Findings

Transverse magnetic correlations can induce thermal hysteresis in electric polarization.

Magnetic correlations affect the free energy landscape of ferroelectric solutions.

Results are applicable to complex multiferroic systems beyond the simple model used.

Abstract

We use a Green's function method with Random Phase Approximation to show how magnetic correlations may affect electric polarization in multiferroic materials with magnetic-exchange-type magnetoelectric coupling. We use a model spin 1/2 ferromagnetic ferroelectric system but our results are expected to apply to multiferroic materials with more complex magnetic structures. In particular, we find that transverse magnetic correlations result in a change in the free energy of the ferroelectric solutions leading to the possibility for thermal hysteresis of the electric polarization above the magnetic Curie temperature. Although we are motivated by multiferroic materials, this problem represents a more general calculation of the effect of fluctuations on coupled order parameters.