Magnetic parameters in giant magnetoresistance spin valve and their roles in magnetoresistance sensitivity

Abstract

Giant magnetoresistance (GMR) spin valves are fabricated and their m(H) (m and H are the magnetic moment and applied magnetic field, respectively) and MR(H) (MR is the magnetoresistance) curves are characterized, from which various magnetic parameters including the interlayer coupling field, the anisotropy field of the free and pinned layers, and the exchange bias field of the pinned layer are extracted. A more accurate exchange bias field is obtained by utilizing an analytical equation for the total energy describing the GMR spin valve. The exchange bias field is found to be greater than the bias of the pinned layer magnetization switching obtained from the experimental m(H) loops, with the difference being proportional to the product of the interlayer coupling field and the free layer magnetization. Among the magnetic parameters, the interlayer coupling field is the dominant factor affecting the sensitivity, which is the most important parameter in sensor applications. The anisotropy field of the free layer is the next important parameter in affecting the sensitivity, but its role is significantly less dominant, being only 15% of the role by the interlayer coupling field.