Mechanism of Lattice-Distortion-Induced Electric-Polarization Flop in the Multiferroic Perovskite Manganites

TL;DR

This paper theoretically investigates the phase diagrams of certain multiferroic manganites, revealing how lattice distortions induce a polarization flop through competing magnetic interactions.

Contribution

It introduces a microscopic model and Monte-Carlo analysis to explain the electric polarization flop driven by lattice distortions in multiferroic perovskite manganites.

Findings

Reproduces magnetoelectric phase diagrams with two multiferroic states.

Identifies the competition between single-ion anisotropy and Dzyaloshinsky-Moriya interaction as the cause of polarization flop.

Shows the polarization change aligns with experimental observations.

Abstract

Magnetoelectric phase diagrams of the perovskite manganites, Eu1-xYxMnO3 and Gd1-xTbxMnO3, are theoretically studied. We first construct a microscopic model, and then analyze the model using the Monte-Carlo method. We reproduce the diagrams, which contain two different multiferroic states, i.e., the ab-plane spin cycloid with electric polarization P//a and the bc-plane spin cycloid with P//c. We reveal that their competition originates from a conflict between the single-ion anisotropy and the Dzyaloshinsky-Moriya interaction, which is controlled by the second-neighbor spin exchanges enhanced by the GdFeO3-type distortion. This leads to a P flop from a to c with increasing x in agreement with the experiments.