Write Characteristics of Thin-Film Heads in a High-Frequency Region.

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Abstract
The write characteristics of thin-film inductive heads in the high-frequency region were examined through R/W testing, recorded bit observation, and dynamic field analysis, and their relations to the pole materials were studied. A thin-film head using a low-resistivity pole, ρ=16 μΩ-cm, could not write data when the frequency was over 40 MHz. Eddy currents in the pole, which cause a phase lag in the recording field to the drive current, were thought to be the reason for this degraded write performance. The amount of the phase lag varied according to the part of the pole, and reached about 5 ns at the track center when the frequency was 20 MHz. Application of a high-resistivity pole material, ρ=90 μΩ-cm, was very effective in decreasing the eddy current loss. In this case, the phase lag of the recording field to the drive current was less than 1 ns at 20 MHz, and data could be written when the frequency was over 90 MHz.

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