Coupling of replicate order-parameters in incommensurate multiferroics

TL;DR

This paper investigates how the coupling of order-parameter replicates in incommensurate multiferroics influences phase transitions and symmetry breaking, using iron vanadate as a case study to reveal the role of spin interactions in ferroelectric stabilization.

Contribution

It provides a detailed analysis of the coupling effects of order-parameter replicates in incommensurate multiferroics, highlighting the critical behavior and symmetry changes during phase transitions.

Findings

Dephasing induces a new broken symmetry phase.

Transition involves critical variation of spin angles.

Isotropic exchange stabilizes the ferroelectric phase.

Abstract

The specific properties of incommensurate multiferroic phases resulting from the coupling of order-parameter replicates are worked out using the illustrative example of iron vanadate. The dephasing between the order-parameter copies induces an additional broken symmetry phase corresponding to the lowest symmetry of the system and varies critically at the transition to the multiferroic phase. It reflects the temperature dependence of the angle between paired spins in the antiferromagnetic spiral structure. Expressing the transition order-parameters in terms of spin-density waves allows showing that isotropic exchange interactions contribute to the stabilization of the ferroelectric phase.