Complete Magnetic Anisotropy Films for Perpendicular Recording Prepared by an Electroless Plating Method

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Abstract
A complete magnetic anisotropy film was formed by an electroless plating method for a high-density perpendicular recording medium. The Co alloy plating bath, using ammoniacal malonate–tartrate–succinate mixed complexing agents was studied mainly by varying three main metal ion factors in the bath: i.e., the concentrations of NiSO4, NH4ReO4, and MnSO4. The fine columnar structure of magnetic film in a cross section was confirmed by SEM observation. Three different kinds of eight-inch disks A, B, and C, were prepared under selected conditions with magnetic film thickness of 0.50, 0.25, and 0.20 μm respectively. The recording performance was evaluated with a Winchester ring head with a 0.33 μm gap length under various head-medium spacings. A perpendicular recording mode was confirmed, and the following recording densities were obtained: D50=54 and 58 kFRPI for disk A, and 57 and 63 kFRPI for disk B when using 0.20 and 0.15 μm practical usable spacing respectively, and D50=68 kFRPI for disk C when using the more advanced 0.12 μm spacing. It was suggested that the electroless cobalt alloy plating has a high potential as a process for producing perpendicular recording media.

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