Symmetry and magnetoelectric interactions in BaMnF4
A.K. Zvezdin and A.P. Pyatakov
A.M. Prokhorov General Physics Institute of RAS, 38 Vavilov Str., Moscow 119991, Russia
Received November 5, 2009, reviced December 7, 2009
Magnetic anisotropy and magnetoelectric interactions in ferroelectric antiferromagnet BaMnF4 are considered theoretically using the symmetry analysis. It is shown that the symmetry allows the existence of inhomogeneous magnetoelectric (flexoelectric type)
interaction possessing a characteristic dependence on value and orientation of external magnetic field. As the field is increased this interaction at critical field
leads to the phase transition to the magnetic incommensurate phase accompanied with a jump of electricpolarization. The linear and quadratic magnetoelectric effects and the relativistic tilt of the magnetic sublattices caused by the magnetoelectric interaction are considered. The proposed technique is a natural generalization of the symmetry analysis to the class of crystals which undergo the phase transitions followed
by a doubling of the unit cell and can be applied not only to the BaMnF4.
PACS: 75.85.+t Magnetoelectric effects, multiferroics; PACS: 77.80.–e Ferroelectricity and antiferroelectricity.
Key words: multiferroics, ferroelectromagnets, incommensurate structure, linear magnetoelectric effect.