Dual exchange biased NiFe-TbCo unshielded MR heads for high density recording

Narrow-trackwidth unshielded MR (magnetoresistive) heads with both longitudinal and transverse bias supplied by a single TbCo exchange-bias layer were constructed. These preliminary dual-biased NiFe-TbCo MR heads exhibit Barkhausen-noise-free, low-distortion response characteristics over a wide range of recording densities (up to 80 kFCI). A 64-μm track width, 7-μm height dual-exchange-biased element exhibited a phase margin of 50% at a raw bit error rate of 10^-5 in a recording channel reproducing (1,7)-coded data written at 40 kFCI (54 kbPI) using compact spectrum write equalization. These exchange-biased head response data compare favorably to data obtained from an unshielded MR head biased by external permanent magnets. The dual-exchange-biased NiFe-TbCo MR heads exhibit a small dependence of bias on temperature (0.3% reduction per °C) and a small reduction in signal (1.3 dB) due to the shunting effect of the TbCo