PRODUCTION OF MAGNETIC RECORDING MEDIUM

PURPOSE:To improve the reproducibility of the coercive force of the titled magnetic recording medium and to improve the squareness ratio of the hysteresis loop by oxidizing the plated surface of a substrate before a gamma-Fe2O3 thin film is formed by a reactive sputtering method. CONSTITUTION:An Ni-Cu-P alloy layer is provided on an aluminum alloy substrate by electroless plating as the disk substrate, the surface is specularly finished and washed to clean the surface and the disk substrate is then placed in a vacuum vessel. Then gaseous oxygen is introduced into the vessel, a voltage is impressed between electrodes arranged in the vessel to generate electric discharge and the disk substrate is exposed to exygen plasma. The substrate is then preheated and placed in a sputtering chamber, an Fe3O4 thin film is formed by reactive sputtering, the film is heated at 300 deg.C for 3hr in the atmosphere and a gamma-Fe2O3 thin film medium is obtained. Consequently, the squareness ratio of the hysteresis loop of the magnetic recording medium is improved and the variance of Hc can be reduced.