Analysis of Angular Dependent Resistance Measurements on IrMn-Based Spin Valves Using a Finite Pinning Model

Abstract—The magnetoresistance of IrMn based spin valve sheet films has been measured as a function of applied field orientation and temperature. Analysis of these angular resolved results allows the separation of the magnetic response of each ferromagnetic layer in the structure. Specifically, the data are fitted to a model of magnetoresistive response that accounts for giant magnetoresistance (GMR) effects between the two layers and anisotropic magnetoresistance (AMR) effects within each layer. Both the pinned and free ferromagnetic layers are assumed to be single domains. Additionally, the free layer is assumed to follow the applied field, while the pinned layer follows the vector sum of the applied field and the pinning field. From the fitting results, several parameters are separated quantitatively, including the resistance change associated with GMR and AMR effects, the misalignment angle for the pinned layer, the angular excursion of the pinned layer under external field, the average current direction and the thermal coefficient of resistance. This analysis can support the design of spin valve readers, especially when extended to the determination of the canting angle of the pinned direction for patterned devices. Index Terms—AMR, angular dependent measurement, anisotropy magnetoresistance, canting angle, giant magnetoresis-tance (GMR), IrMn, magnetic recording heads, memory device, spin valve. I