Bond distortion effects and electric orders in spiral multiferroic magnets

TL;DR

This paper investigates how bond distortions influence electric polarization in spiral multiferroic magnets, highlighting the effects on spin-current and lattice-mediated polarization, with calculations on various clusters and applications to cuprates.

Contribution

It introduces a detailed theoretical analysis of bond distortion effects on electric polarization in spiral multiferroics, incorporating cluster models and applying findings to real materials.

Findings

Bond distortion breaks inversion symmetry and modifies $d$-$p$ hybridization.

Electric polarization is affected by bond distortion, influencing spin-current and lattice-mediated parts.

Results agree with experimental observations in cuprate multiferroics.

Abstract

We study in this paper bond distortion effect on electric polarization in spiral multiferroic magnets based on cluster and chain models. The bond distortion break inversion symmetry and modify the $d$-$p$ hybridization. Consequently, it will affect electric polarization which can be divided into spin-current part and lattice-mediated part. The spin-current polarization can be written in terms of $\vec{e}_{i,j}\times(\vec{e}_{i}\times\vec{e}_{j}) $ and the lattice-mediated polarization exists only when the M-O-M bond is distorted. The electric polarization for three-atom M-O-M and four-atom M-O$_{2}$-M clusters is calculated. We also study possible electric ordering in three kinds of chains made of different clusters. We apply our theory to multiferroics cuprates and find that the results are in agreement with experimental observations.