Low-noise metal medium for high-density longitudinal recording

Abstract

A low‐noise medium that shows potential for future high‐density longitudinal magnetic recording applications has been prepared and studied. The disk consists of a CoCr‐based ternary alloy and a few percent of a third transition metal sputter deposited on a Cr underlayer. The media noise power is low and nearly frequency independent up to 80 kfci, in sharp contrast to the noise power spectra typical of metal films. Because of the exceptionally low media noise, we have obtained signal‐to‐noise ratios (SNR) greater than 35 dB up to 30 kfci on media having a 70% amplitude density (D₇₀) of 20 kfci. Other characteristics of the media include overwrite better than −35 dB, saturation magnetization of 500 emu/cm³, and coercivity of 1300 Oe. The grain diameter, coercivity, and D₇₀ depend strongly upon the Cr underlayer thickness. The data suggest that the low‐noise results from reduced intergranular exchange coupling.