Spin-current model of electric polarization with the tensor gyromagnetic ratio

TL;DR

This paper extends the spin-current model of electric polarization to include tensor gyromagnetic ratios, proposing three mechanisms of magnetoelectric effects and predicting new polarization solutions in complex spin orders.

Contribution

It introduces a generalized spin-current model incorporating tensor g-factors, revealing new polarization effects in magnetic structures with anisotropic g-tensors.

Findings

Derived the dependence of electric polarization on spin density and tensor g-factor.

Predicted new macroscopic electric polarization solutions in cycloidal and helicoidal spin orders.

Extended the spin-current model to include effects relevant for magnetic ferroelectrics with heavy ions.

Abstract

The spin-current model of electric polarization of spin origin is developed for a magnetic structure with anisotropic tensor gyromagnetic ratio (g-factor). Three mechanisms of the magnetoelectric effect are proposed, caused by the symmetric Heisenberg exchange interaction, the Dzyaloshinsky-Moriya interaction, and the spin-spin interaction related to the odd anisotropy of the symmetric exchange interaction of magnetic ions via nonmagnetic ion. The dependence of electric polarization on the spin density and tensor g-factor in the generalized spin-current model is derived. New solutions for macroscopic electric polarization, that arise in the cycloidal and helicoidal spin orders and are caused by the non-diagonal components of the gyromagnetic ratio, are predicted. The extended of the spin-current model to including a tensor g-factor can be important for the magnetic ferroelectrics with heavy ions which take part in the formation of magnetoelectric effect.