Effect of Antiferromagnetically Coupled Thin Surface Layers on Coercivity of A Magnetically Hard Grain - Numerical Calculation

摘要

The effects of a thin ferromagnetic layer covering a magnetically hard grain on the coercivity were calculated based on micromagnetic theory. Antiferromagnetic exchange coupling between this thin ferromagnetic surface layer (SF layer) and the hard grain was found to prevent nucleation of reverse domains at the surface of the hard grain and to increase the coercivity. This was effective for hard grains with a layer of reduced magnetic anisotropy on their surfaces whose thickness is comparable with the exchange length. It was also found that a suitable thickness of a SF layer depends on the saturation polarization of the SF layer and is approximately several nanometers.