| 摘要 |
PURPOSE:To record and erase uniformly with the same laser power at the inner periphery and at the outer periphery by forming a magnetic film so that the Curie temp. of the film is successively reduced from the inner peripheral part toward the outer peripheral part by changing the composition. CONSTITUTION:A photomagnetic disk substrate 1 to be provided with a recording medium is set on the cathode side of a device and a target 2 is placed on the anode side and connected to a high-voltage power source 3. The device is evacuated and sputtering is carried out in the atmosphere of an inert gas such as gaseous Ar to form an amorphous film of an alloy constituting the target 2 on the magnetic disk substrate 1. The target 2 is obtained by arranging a pellet 5 consisting of Co and a pellet 6 consisting of Tb on an Fe sheet 4. The Co pellets are arranged so that the density is successively decreased from the inner peripheral part toward the outer peripheral part and the Tb pellets are uniformly arranged. Consequently, a recording medium whose Curie temp. is successively lowered from the inner periphery toward the outer periphery, the recording and erasing can be carried out with the constant laser power, the mechanism of an optical disk is simplified.
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