Patent ID: 7580229

Claim:
A magnetoresistive sensor having first and second electrical leads for connection to a current source that directs sense current from the first lead to the second lead, the sensor having a stack of layers between the first and second leads comprising: one and only one pinned ferromagnetic layer having an in-plane magnetization direction; an antiparallel free (APF) structure consisting of a first free ferromagnetic layer (FL 1 ) having an in-plane magnetization direction, a second free ferromagnetic layer (FL 2 ) having an in-plane magnetization direction substantially antiparallel to the magnetization direction of FL 1 and a magnetic moment less than that of FL 1 , and an AP coupling (APC) layer between and in contact with FL 1 and FL 2 and consisting essentially of a material selected from the group consisting of Ru, Ir, Rh and alloys thereof; and an electrically conductive spacer layer between the pinned ferromagnetic layer and FL 1 and consisting essentially of an element selected from the group consisting of Cu, Ag and Au, the pinned ferromagnetic layer being located between the spacer layer and the first lead; and wherein the sensor senses external magnetic fields in response to sense current applied perpendicular to the planes of the layers in the sensor stack in a direction from the first lead to the pinned ferromagnetic layer to the spacer layer to the APF structure and to the second lead.