Spin model of magnetostrictions in multiferroic Mn perovskites

TL;DR

This paper develops a realistic spin model for multiferroic Mn perovskites, revealing the significant role of symmetric magnetostriction in ferroelectricity and predicting complex spin structures.

Contribution

It introduces a comprehensive spin-phonon coupled model that reproduces experimental phase diagrams and uncovers the importance of symmetric magnetostriction in multiferroic behavior.

Findings

Symmetric magnetostriction significantly contributes to ferroelectricity.

The model accurately reproduces the experimental phase diagram.

Prediction of noncollinear deformation and coexistence of E and spiral states.

Abstract

We theoretically study origins of the ferroelectricity in the multiferroic phases of the rare-earth (R) Mn perovskites, RMnO3, by constructing a realistic spin model including the spin-phonon coupling, which reproduces the entire experimental phase diagram in the plane of temperature and Mn-O-Mn bond angle for the first time. Surprisingly we reveal a significant contribution of the symmetric (S.S)-type magnetostriction to the ferroelectricity even in a spin-spiral-based multiferroic phase, which can be larger than the usually expected antisymmetric (SxS)-type contribution. This explains well the nontrivial behavior of the electric polarization. We also predict the noncollinear deformation of the E-type spin structure and a wide coexisting regime of the E and spiral states, which resolve several experimental puzzles.