# On the magnetoelastic and magnetoelectric couplings across the antiferromagnetic transition in multiferroic BiFeO3

## TL;DR

This study investigates the elastic and lattice anomalies in BiFeO3 across its antiferromagnetic transition, revealing magnetoelastic and magnetoelectric couplings through experiments and theoretical modeling.

## Contribution

It combines experimental measurements with first-principles calculations and a Landau-like model to elucidate the couplings affecting elastic properties at T_N in BiFeO3.

## Key findings

- Anomalies in lattice thermal expansion at T_N
- Elastic softening observed at the magnetic transition
- Magnetostriction and couplings explain elastic behavior

## Abstract

Clear anomalies in the lattice thermal expansion (deviation from linear variation) and elastic properties (softening of the sound velocity) at the antiferromagnetic-to-paramagnetic transition are observed in the prototypical multiferroic BiFeO3 using a combination of picosecond acoustic pump-probe and high-temperature X-ray diffraction experiments. Similar anomalies are also evidenced using first-principles calculations supporting our experimental findings. Those calculations in addition to a simple Landau-like model we also developed allow to understand the elastic softening and lattice change at T_N as a result of magnetostriction combined with electrostrictive and magnetoelectric couplings which renormalize the elastic constants of the high-temperature reference phase when the critical T_N temperature is reached.