The Dependence of the Corrosion Behavior of Rigid Disk Magnetic Recording Media on the Deposition Conditions of the Underlayer, Magnetic Layer, and Carbon Overcoat

Abstract

The electrochemical response of thin‐film rigid‐disk samples of magnetic recording media prepared by dc magnetron sputtering and immersed in 3% (mass) aqueous solution was investigated. The disk samples had the general formulation; some were tested without the carbon overcoat. The argon pressure and sputtering power during sample preparation were varied between 0.66 and 2.0 Pa and between 1.6 and 4.8 W/cm2, respectively. Electrochemical impedance analysis and linear sweep voltammetry yielded values for the double‐layer capacitance and the faradaic resistance of each sample. The crucial finding was that the deposition conditions of the chromium underlayer determined the corrosion properties of the films; an argon pressure of 0.66 Pa and RF power of 4.8 W/cm2 for the Cr deposition yielded corrosion‐resistant films, but values of 2 Pa and 1.6 W/cm2 yielded easily corroded films (deposition conditions of the other layers being held constant). The corrosion‐resistant films were flat, relatively featureless, and the c‐axis of the grains of alloy was in the plane of the thin film. The films susceptible to corrosion were rough with sharp edges and possible microgaps in the carbon layer, and the c‐axis of the magnetic layer was perpendicular to the plane.