| 摘要 |
PURPOSE:To average S/N over the entire surface by providing a magnetic layer which consists essentially of gamma-Fe2O3, is incorporated therein with Cu, Ti and Co, contg. Cu in a specific concn. range and having the concn. of Cu increasing continuously from the outside circumferential part of the disk toward the inside circumferential part on a non- magnetic disk substrate. CONSTITUTION:The magnetic layer which consists essentially of gamma-Fe2O3 and is incorporated with Cu in order to decrease noise, Ti in order to increase the temp. margin in the stage of forming a film and Co in order to increase coercive force is formed by a sputtering method on the disk-shaped substrate, more particularly Al, glass or ceramic substrate. If the amt. of the Cu to be added is increased in this stage, the crystal grain size of gamma-Fe2O3 decreases and the S/N ratio increases but the grain boundary is made less stronger and softer than the crystal part and is thus made vulnerable to damage by a magnetic head. The outside circumference of the disk is made particularly susceptible to a damage. Cu is incorporated into the magnetic layer at 0.1-5at% over the entire part thereof and is so incorporated that the concn. thereof decreases from the outside circumferential part toward the inside circumferential part in order to prevent the above-mentioned damage. The S/N over the entire surface of the disk is thus averaged and the noise is reduced overall. Durability is improved as well.
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