New surface structures and spin-reorientation phase transitions in anisotropic magnetic superlattices
Zvezdin A. K. , Utochkin S. N.
Spin-reorientation phase transitions in anisotropic ferrimagnetic superlattices are analyzed. Expressions for the critical lines for second-order phase transitions are derived in the limit of an infinite number of layers for the case of magnetization along a hard axis. A μ-h phase diagram is constructed. Here μ is the relative magnetic moment of a unit cell of the superlattice, and h is the reduced external field. The external surface has a strong effect on the magnetic state of the superlattice. In particular, it leads to new surface magnetic phases. Whether the surface layer is isotropic or anisotropic is also an important factor.