Influence of particle interaction on coercivity and squareness of thin film recording media

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Abstract
Digital Recording density in continuous thin films can be significantly larger than in conventional particulate media. For this reason, there is much active research and development in such thin film recording media at present. However, no detailed calculation leading to a satisfactory explanation for the high squareness and an Hc decreasing monotonically with film thickness t has appeared. Using a model of strongly interacting anisotropic grains and neglecting exchange at grain boundaries, we examined here particle interaction and its influence on S and Hc. It is shown that the rather high squareness found in such media (e.g., S?0.8 for films of Co with t≳200Å) is related to strong dipolar interaction between the constituent grains. Although such films are continuous, surface roughness due to microscopic film thickness variation from grain to grain‐boundary can be appreciable. Indeed, our calculation shows that these thickness variations can account for Hc and its variation with t experimentally observed.

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