First-principles study of improper ferroelectricity in TbMnO3

TL;DR

This study uses first-principles calculations to analyze the magnetically induced polarization in TbMnO3, revealing the dominance of lattice contributions and providing insights into the underlying mechanisms of improper ferroelectricity.

Contribution

It presents a detailed first-principles analysis of the electronic and lattice contributions to polarization in TbMnO3, highlighting the limitations of simple models based on Dzyaloshinskii-Moriya interactions.

Findings

Lattice-mediated polarization is strongly dominant in TbMnO3.

Computed polarization aligns well with experimental data.

Simple nearest-neighbor Dzyaloshinskii-Moriya models are insufficient.

Abstract

We have carried out a first-principles theoretical study of the magnetically induced polarization in orthorhombic TbMnO3, a prototypical material in which a cycloidal spin structure generates an electric polarization via the spin-orbit interaction. We compute both the electronic and the lattice-mediated contributions to the polarization and find that the latter is strongly dominant. We analyze the spin-orbit induced forces and lattice displacements from both atomic and mode-decomposition viewpoints, and show that a simple model based on nearest Mn--Mn neighbor Dzyaloshinskii-Moriya interactions is not able to account fully for the results. The direction and magnitude of our computed polarization are in good agreement with experiment.