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A longitudinal bias method using a long distance exchange coupling field, which was observed between an IrMn layer and a NiFe/CoFe bilayer across a Cu interlayer, has been investigated for magnetic read heads. The exchange coupling field could be changed in the layered film consisting of Ta/NiFe/Cu(0, 1.0, 1.5, 2.0 nm)/IrMn. In order to align the easy axes of the free and pinned ferromagnetic layers perpendicular to each other, a two-step annealing process was carried out to rotate the easy axis of the free layer in the tunnel magnetoresistive read heads. The angle between the two easy axes was 72° in the junction after an optimized two-step annealing. The tunnel magnetoresistive readers, which have a resistance×area product of about 2000 Ω μm2 and a tunnel magnetoresistance ratio of about 15%, showed an output voltage of 9080 μVp−p and 2270 μVp−p/μm, which was comparable to that of a typical giant magnetoresistive reader for a 7.5 Gbits/in.2 hard disk drive. © 2001 American Institute of Physics.
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