Spin valve sensors with synthetic free and pinned layers

Unshielded spin-valve sensors (6 x 2 mu m(2)) with both synthetic ferrimagnet free (SF) and synthetic antiferromagnet pinned (SAF) layers are demonstrated, exhibiting high sensitivities, good thermal stability and reduced free layer effective magnetic thickness (t(eff)). The free layer t(eff) can be reduced to similar to 10 Angstrom while maintaining its physical thickness near 60 Angstrom, without significant magnetoresistive signal loss (MR similar to 6%). After current biasing, the sensors show a linearized response, demonstrating a coherent switching of the synthetic free layer. Sensor sensitivity (S) increases with decreasing free layer effective magnetic thickness (S approximate to 0.5%/Oe at t(eff) = 10 Angstrom) as expected from the decrease of the free layer demagnetizing field. The coupling field (H-f) between the free and pinned layers increases with decreasing t(eff) (H(f)proportional to M-s(2)/(t(eff)M(eff)(f))). The sensors are thermally stable upon anneals up to 300 degrees C. (C) 2000 American Institute of Physics. [S0021-8979(00)74208-3].