Improved bias and stability in dual-exchange-biased unshielded magnetoresistive heads

Data are presented on dual-exchange-biased NiFe-TbCo UMR (unshielded magnetoresistive) tape heads with improved signal response and process stability. It was found that a Si/sub 3/N/sub 4/ passivation layer offered better stability of the exchange bias through head processing than SiO/sub 2/. In order to improve sensor sensitivity, the longitudinal component of the exchange bias was reduced by increasing the exchange angle to 75 degrees from the sense current direction. This resulted in a +6-dB improvement in signal over previous heads without sacrificing Barkhausen-noise-free operation in narrow trackwidths. Heads with trackwidths as narrow as 8 mu m were shown to operate at linear densities of up to 50 kFCI with excellent signal-to-noise ratios (>45 dB). Investigations of different passivation materials showed Si/sub 3/N/sub 4/ to provide the best protection against environmental corrosion and thermally induced oxidation of the TbCo layer.<
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