FePt Grain Size Limit and Required Switching Field in the Presence of Surface Anisotropy

Surface anisotropy that opposes crystalline anisotropy can become significant for highly packed grains. In this paper, we present an estimation of FePt grain size limit in the presence of surface anisotropy. The estimated grain size is optimized for rectangular, circular and hexagonal grain, respectively. In this manner, the thermally stable granular media can be attained for high areal density magnetic recording system. Micromagnetic simulations are performed to predict the required switching field for FePt granular media in the presence of surface anisotropy. The results reveal possible engineering challenges faced in designing high density magnetic recording medium.