Role of Grain Boundaries in the Coercivity of Magnetic Thin Films Investigated by a Two-Dimensional Ginzburg-Landau-Type Model

We investigate a two-dimensional Ginzburg-Landau-type model, with focus on grain boundaries that are prevalent in magnetic thin films with perpendicular magnetic anisotropy. The model covers four basic interactions, which are exchange, anisotropic, external, and dipole-dipole interactions, and describes magnetic thin films. Through numerical simulations for square grains, we find that there is a minimum grain-grain distance beyond which the interactions effectively vanish. Furthermore, we also find that magnetic reversals occur at the corners of grains and confirm that circular grains result in higher coercivity under similar packing ratio, because of the absence of corners.