A current-perpendicular-to-the-plane (CPP)
magnetoresistive sensor has an antiparallel free (APF) structure as the free layer and a specific direction for the applied bias or sense current. The (APF) structure has a first free ferromagnetic (FL1), a second free ferromagnetic layer (FL2), and an antiparallel (AP)
coupling (APC) layer that couples FL1 and FL2 together antiferromagnetically with the result that FL1 and FL2 have substantially antiparallel
magnetization directions and rotate together in the presence of a
magnetic field. The thicknesses of FL1 and FL2 are chosen to obtain the desired net free layer
magnetic moment / area for the sensor, and the thickness of FL1 is preferably chosen to be greater than the spin-
diffusion length of the electrons in the FL1 material to maximize the bulk spin-dependent scattering of electrons and thus maximize the sensor
signal. The CPP sensor operates specifically with the conventional sense current (opposite the
electron current) directed from the pinned ferromagnetic layer to the APF structure, which results in suppression of current-induced
noise.