Patent ID: 8014109

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; an antiparallel (AP) pinned structure on the substrate and comprising a first AP-pinned (AP1) ferromagnetic layer having an in-plane magnetization direction, a second AP-pinned (A2) ferromagnetic layer having an in-plane magnetization direction substantially antiparallel to the magnetization direction of the AP1 layer, the AP2 layer being a multilayer comprising a first AP2-1 sublayer and a second AP2-2 sublayer, and an AP coupling (APC) layer between and in contact with the AP1 layer and the first AP2-1 sublayer; a free ferromagnetic layer having an in-plane magnetization direction substantially free to rotate in the presence of an external magnetic field; and a spacer layer between and in contact with the free ferromagnetic layer and the second AP2-2 sublayer; wherein the second AP2-2 sublayer comprises a ferromagnetic alloy comprising Co, Fe and Si, wherein Si is present in the alloy in an amount greater than or equal to 20 atomic percent and less than or equal to 30 atomic percent and the ratio of Co to Fe in the alloy is between about 0.8 and 1.2; and wherein the first AP2-1 sublayer in contact with the APC layer contains no Si.