Influence of coercivity squareness on media noise in thin-film recording media

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Abstract
Signal and media noise measurements have been made for a wide variety of Co-alloy longitudinal magnetic recording media. A strong correlation between media noise and the coercivity squareness, S*, is observed at high transition density. The optimum ratio of isolated pulse amplitude to media noise is found for S*≂0.75. This behavior arises from reduced ferromagnetic exchange coupling between neighboring grains of the film which influence both the coercivity squareness and also the uniformity of the domain boundary at the recorded transitions. The low-noise characteristics of sputtered γ-Fe2O3 also appear to correlate with low values of coercivity squareness. This work confirms that for systems in which media noise is a limiting factor, optimum performance may require considerably lower values of coercivity squareness than commonly used, determined by the relative contribution of media noise to the overall system noise.