ANNEALING EFFECT ON SPIN-VALVE SENSOR TRANSFER CURVES

Unshielded spin-valve sensors were fabricated and annealed to study th e effect of high temperature processing on the transfer curves. A micr omagnetic simulation program was developed to analyze the changes obse rved on the transfer curves upon annealing, Analysis of experimental d ata versus the micromagnetic simulations indicates two causes responsi ble for the progressive loss of the MR signal upon annealing above the blocking temperature: a rotation of the pinned layer magnetization fr om the transverse to the longitudinal direction (along the sensor trac kwidth) and an increase of the free layer anisotropy, Rotation of the free layer easy axis can also be observed, Cool down in a magnetic fie ld can prevent this MR loss by pinning the magnetization direction dur ing the high temperature stage.