Spontaneous toroidic effects in Ba2CoGe2O7

TL;DR

This paper investigates the spontaneous toroidal effects in Ba2CoGe2O7, revealing how the toroidal moment influences magnetoelectric properties in its multiferroic phase below 6.7K.

Contribution

It demonstrates the role of the spontaneous toroidal moment in multiferroic Ba2CoGe2O7 and links it to observable magnetoelectric effects and single-ion contributions.

Findings

Spontaneous toroidal moment exists below 6.7K in Ba2CoGe2O7.

Toroidic effects contribute to polarization and magnetization.

Single-ion effects influence the toroidic contribution to polarization.

Abstract

The unusual magnetoelectric effects observed in the multiferroic phase arising below TN=6.7K in Ba2CoGe2O7 (BCG) are related to the spontaneous toroidal moment existing in this compound. The transition to the multiferroic state, which involves spontaneous magnetization, polarization and toroidal moment gives rise to spontaneous toroidic effects. These effects produce specific contributions to the spontaneous polarization and magnetization under applied magnetic or electric fields which provide indirect indications of the existence and role of the toroidal moment in multiferroic materials. The toroidic contribution to the electric polarization in BCG is shown to result from single-ion effects.