Micromagnetism of patterned ferromagnetic thin films with four-fold anisotropy

Micromagnetic configurations of structured magnetic thin films with the four fold crystalline anisotropy have been systematically studied with numerical simulations. Two different remanence states of leaf and vortex-antivortex pairs are observed in a square pattern with lateral dimension of several tenths μm, depending on the magnitude of anisotropy energy. The threshold value of the anisotropy between these two states increases with the decrease of lateral dimension. Two orders of susceptibility difference is demonstrated in the leaf configuration for the two different orthogonal AC filed directions.