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, w hich was observed between an IrMn layer and a NiFe/CoFe bilayer across a Cu interlayer, has been investigated for magnetic read heads. The exchange co upling 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 anneali ng 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 wa s 72 degrees in the junction after an optimized two-step annealing. The tun nel 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 compara ble to that of a typical giant magnetoresistive reader for a 7.5 Gbits/in.( 2) hard disk drive. (C) 2001 American Institute of Physics.