Patent ID: 7957107

Claim:
A magnetoresistive sensor having electrical leads for connection to a source of sense current and comprising: one and only one pinned ferromagnetic layer having an in-plane magnetization direction; an antiparallel free (APF) structure comprising a first free ferromagnetic layer (FL 1 ) having an in-plane magnetization, a second free ferromagnetic layer (FL 2 ) having an in-plane magnetization substantially antiparallel to the magnetization 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, wherein FL 2 has a thickness equal to or greater than a thickness that results in a FL 2 magnetic moment equivalent to 10 Å Ni 80 Fe 20 ; 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; and wherein the sensor is capable of sensing external magnetic fields when a sense current is applied perpendicular to the planes of the layers in the sensor in a direction from the pinned ferromagnetic layer to the APF structure.