Magnetization processes in ferromagnetic nanostructures with competing anisotropies

A micromagnetic framework based on the phenomenological theory for induced magnetic interactions is developed to analyse states in ferromagnetic nanolayers under competing intrinsic and (uniaxial, unidirectional) surface-induced anisotropies. Magnetic phase diagrams in components of applied fields show complex systems of critical lines and lines of first-order transitions corresponding to two-phase and multiphase coexistence regions. The role of these first-order transitions for multidomain states and limiting cases of the corresponding magnetization processes are discussed. The inhomogeneous distribution of induced magnetic anisotropies across the thickness of a layer may occasion non-collinear magnetic states.