| 摘要 |
PURPOSE:To improve productivity and durability by utilizing a high-permeability material for the substrate of a disk type vertical magnetic recording medium. CONSTITUTION:MnZn ferrite which has 5 inch diameter, consists essentially of Mn0.5Zn0.5Fe2O4, has 1.5mm. thickness, is finished to a specular surface and is heat-treated at 1,100-1,200 deg.C is used as the substrate 4, on which 0.2mu Co-Cr layers 1, 1', are deposited by sputtering. Substantial strength is obtd. with such MnZn ferrite plate 4 having the thickness of about 2/3 the thickness of the conventional aluminum plate. Since the specific weight thereof is less than two times the specific gravity of the aluminum, the entire weight of the disk is made within about 1.4-times the weight of the conventional disk.
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