Theory of induced uniaxial anisotropy in magnetic nanostructures

A phenomenological theory of surface-induced magnetic anisotropy and corresponding micromagnetic equations to calculate equilibrium magnetic states are presented for different shapes of magnetic nanostructures embedded into nonmagnetic media (films, cylindrical dots and wires, and spherical nanoparticles). In magnetic nanowires the induced anisotropy causes a continuous reorientation transition at a critical radius from the homogeneous state to a vortex state.