A soft-magnetic ferrite disk substrate was investigated as an underlayer of perpendicular double layer hard disk media for single-pole heads. Although a soft-magnetic thin-film is generally used for the underlayer, concern about the eddy current effect for a metallic underlayer in high-frequency operations. In order to avoid the eddy current, Co-Cr perpendicular media were prepared on the Mn-Zn ferrite substrate to examine their read/write performance. Experimental results with a single-pole writing head and an MR head showed that the ferrite substrate disk had better writing sensitivity and frequency response owing to its large volume and electrical resistivity.
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