Mn substitution provides perfect perturbation on the local structure and electronic behavior of BiFeO3. The crystal structure of BiFe1−xMnxO3 (0 ⩽ x ⩽ 0.3) changes from rhombohedral R3c to orthorhombic Pbnm via a biphasic region with increasing x. It is found that Mn doping leads to the depolarization of the Bi–O configuration, and the Jahn–Teller distortion of Fe/MnO6 octahedra. An enhancement of remanent magnetization of BiFe1−xMnxO3 is observed.

The magnetic relaxation of the disordered exchange interacting random anisotropy systems is investigated based on the Monte Carlo method. Similar to the dipolar interacting systems [M. Ulrich, J. García-Otero, J. Rivas, A. Bunde, Phys. Rev. B 67 (2003) 024416], the logarithmic relaxation rate decays by a universal power law, W(t)=At−n. The exponent n increases monotonically with the decreasing temperature as well as the increasing exchange interaction. Depending on the value of n, short-range ferromagnetic correlations (or spin-glass-like behaviour) and superferromagnetic order are suggested.