Effect of ferromagnetic and ferroelectric properties on the sound velocity anomaly in BiFeO3

Abstract The effect of ferromagnetic and ferroelectric properties on the sound velocity in multiferroic BiFeO 3 (BFO) is studied with using Green’s function method on the basis of the magnetoelectric coupling, the spin-phonon interaction and the anharmonic phonon-phonon interaction. The Heisenberg-like model is employed to describe the magnetic subsystem, and the transverse Ising model is used to explain the ferroelectric subsystem. The reduced velocity is obtained in the limit of zero wave vectors. It is shown that the reduced velocity of sound of BiFeO 3 exhibits a cusp-like at the magnetic phase transition temperature T N . This anomaly in reduced velocity can be explained as an influence of vanishing magnetic ordering above T N and the ferroelectric subsystem can not be influenced by the magnetic subsystem above T N due to T N ≪ T C in the BFO. The reduced velocity and T N increase with increasing of the J 1 , J 2 and g , whereas reduced velocity decreases with I increases. The achieved conclusion is in accordance with the experimental results.