Patent ID: 7551409

Claim:
A magnetoresistive sensor capable of sensing external magnetic fields when a sense current is applied perpendicular to the planes of the layers in the sensor, the sensor comprising: a substrate; a pinned ferromagnetic layer having an in-plane magnetization direction; a nonmagnetic spacer layer on and in contact with the pinned layer; and a free layer structure on the nonmagnetic spacer layer and comprising a first ferromagnetic interface layer on and in contact with the nonmagnetic spacer layer, a first electrically conductive interlayer on and in contact with the first interface layer, a central ferromagnetic free layer on and in contact with the first interlayer, a second electrically conductive interlayer on and in contact with the central free layer, and a second ferromagnetic interface layer on and in contact with the second interlayer; the first ferromagnetic interface layer, central ferromagnetic free layer, and second ferromagnetic interface layer being ferromagnetically coupled and having in-plane magnetization directions substantially free to rotate in the presence of an external magnetic field; and each of the first and second ferromagnetic interface layers comprising a (Co x Fe 100-x ) 100-y M y alloy, where M is Al or Si, x is between about 40 and 60 atomic percent and y is between about 20 and 30 atomic percent.