Monte Carlo studies of magnetic phase transitions in (1- x )BiFeO 3 – xA Fe 1/2 M 1/2 O 3 ( A = Pb, Ba, Ca, Sr; M = Nb, Sb) solid solutions

In this work, we theoretically study the magnetic phase transitions in the solid solutions (1-x)BiFeO3 – xAFe1/2M1/2O3 (A = Pb, Ba, Ca, Sr; M = Nb, Sb). We first calculate the magnetic exchange constants using the density functional theory, which are then used in Monte Carlo calculations. We obtain the dependence of magnetic phase transition temperature on x for different cases of the distribution of Fe and M atoms in the B-sublattice of the perovskite structure, i.e. purely statistical distribution, local clustering, and local ordering. Comparison with the experimental data may suggest the change in local arrangement of atoms above x≈0.7 for some compounds.