Spin-polarization coupling in multiferroic transition-metal oxides

TL;DR

This paper develops a microscopic theory for magnetically induced ferroelectricity in transition-metal oxides, identifying key mechanisms and predicting experimental signatures, with a focus on spin-orbit interactions and their role in multiferroic behavior.

Contribution

It introduces a comprehensive microscopic framework for understanding spin-polarization coupling in multiferroic transition-metal oxides, emphasizing the role of spin-orbit interactions on ligand orbitals.

Findings

Spin-orbit interaction on ligand p orbitals induces ferroelectric polarization.

The theory explains the multiferroic properties of TbMnO3.

Predictions for X-ray and neutron scattering experiments are provided.

Abstract

A systematic microscopic theory of magnetically induced ferroelectricity and lattice modulation is presented for all electron configurations of Mott-insulating transition-metal oxides. Various mechanisms of polarization are identified in terms of a strong-coupling perturbation theory. Especially, the spin-orbit interaction acting on the ligand p orbitals is shown to give the ferroelectric polarization of the spin-current form, which plays a crucial role particularly in eg systems. Semiquantitative agreements with the multiferroic TbMnO3 are obtained. Predictions for X-ray and neutron scattering experiments are proposed to clarify the microscopic mechanism of the spin-polarization coupling in different materials.