Micromagnetic Studies of the Effects of Crystalline Anisotropy on the Remanent Magnetization of Ferromagnetic Nanorings

Numerical simulations were performed for thin ferromagnetic nanorings with non-negligible anisotropy. In a thin film, the cubic crystalline anisotropy reduces to a four-fold symmetric term favoring magnetization along the +/-(X) over cap and +/-(Y) over cap directions. Our numerical studies use an extension of the previously proposed algorithm for thin film micromagnetic simulations based on optimal grids for the calculation of the stray field. The relative strength of the magnetostatic energy was varied with respect to the crystalline and exchange energies. The remanent magnetization configurations were obtained for a variety of ring geometries and initial saturation orientations. The magnetocrystalline contribution causes the appearance of distinct domains in the annular structure, resulting in a new variety of magnetization configurations. Based on energetic considerations we provide a classification of possible remanent states.