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The effect of heat treatment on magnetic properties, microstructure, and read-write characteristics of Co-CoO evaporated films are investigated. With heat treatment, the columnar structure in the cross section of films disappears, and perpendicular magnetic anisotropy decreases. However, the shoulder of the M-H curve changes from a rounded to square shape, indicating that the magnetization reverses rapidly. As a result, read-write characteristics improve in spite of the anisotropy decrease. After heating a film having saturation magnetization (Ms) of 1040 kA/m, the output at 80 kFCI (Eeol<) is 300 nV p _ p , and the 50% down recording density (D"o) is 150 kFCI.

We have investigated the Co/Pd multilayer media with a Pd–SiN granular seed layer as perpendicular recording media. The Pd–SiN granular seed layer and the Co(0.2 nm)/Pd(0.8 nm) multilayer were formed by dc and rf sputtering at room temperature on a FeTaC soft magnetic underlayer. The Pd–SiN granular seed layer of 3 nm was very effective to get good magnetic properties with coercivity of 3.9 kOe, a nucleation field of −2.1 kOe, and a M–H slope parameter 4π(dM/dH)H=Hc of 1.4. In addition, it was found that growth of multilayer grains is sensitive to surface conditions of the soft magnetic underlayer. The average column diameter of 13.7 nm with a dispersion of 21.7% was evaluated from the plan-view transmission electron microscope image of well-separated Co/Pd columns with a boundary, which was grown on the Pd–SiN seed layer and the soft magnetic underlayer with Ar plasma etching. Atomic force microscope measurements showed that mean roughness (Ra) of the FeTaC surface decreased from 0.46 to 0.39 nm by the plasma etching. This surface treatment on the soft magnetic underlayer gave better signal to noise ratio by 1.6 dB in playback performance by using of a spin stand with a merged-type ring writer and giant magnetoresistance reader.

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