Weak ferromagnetism discovery at modulated structure destruction for BiFeO3

In this paper the results of experimental and theoretical researches of bismuth ferrite in high magnetic fields that were conducted by the authors in the last decade are considered. The rise of several new effects at the destruction of the space modulated spin structure such as magnetoelectric effect, weak ferromagnetism and toroidal moment were theoretically predicted and proved experimentally. The explanation of the origin of these effects is given. The unique possibility of coexistence of linear magnetoelectrical effect and weak ferromangetic, moment in BiFeO3 at the phase transition to homogenous state is shown. Noteworthy that such a coexistence is not possible for ordinary antiferromagnetics.