Linear roto-antiferromagnetic effect in multiferroics: physical manifestations

TL;DR

This paper predicts a linear roto-antiferromagnetic effect in certain multiferroics, leading to observable physical phenomena like transition smearing and weak antiferromagnetism above the Neel temperature, supported by theoretical and experimental estimations.

Contribution

It introduces the concept of a linear roto-antiferromagnetic effect in multiferroics and identifies conditions for its occurrence, supported by symmetry and microscopic models.

Findings

Predicted the linear roto-antiferromagnetic effect in perovskites.

Identified physical manifestations such as transition smearing and specific heat jumps.

Estimated the effect's magnitude in BiFeO3-based solid solutions.

Abstract

Using the theory of symmetry and the microscopic model we predicted the possibility of a linear roto-antiferromagnetic effect in the perovskites with structural antiferrodistortive and antiferromagnetic long-range ordering and found the necessary conditions of its occurrence. The main physical manifestations of this effect are the smearing of the antiferromagnetic transition and the jump of the specific heat near it. In the absence of external fields linear roto-antiferromagnetic coupling can induce a weak antiferromagnetic ordering above the Neel temperature, but below the temperature of antiferrodistortive transition. Therefore, there is the possibility of observing weak antiferromagnetism in multiferroics such as bismuth ferrite (BiFeO3) at temperatures T>TN, for which the Neel temperature TN is about 645 K, and the antiferrodistortive transition temperature is about 1200 K. By quantitative comparison with experiment we made estimations of the linear roto-antiferromagnetic effect in the solid solutions of multiferroic Bi1-xRxFeO3 (R=La, Nd).