Longitudinal bias method using a long distance exchange coupling field in tunnel magnetoresistance junctions

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 degrees in the junction after an optimized two-step annealing. The tunnel magnetoresistive readers, which have a resistancexarea product of about 2000 Ohm mum(2) and a tunnel magnetoresistance ratio of about 15%, showed an output voltage of 9080 muV(p-p) and 2270 muV(p-p)/mum, which was comparable to that of a typical giant magnetoresistive reader for a 7.5 Gbits/in.(2) hard disk drive. (C) 2001 American Institute of Physics.