Spin valves with canted pinning field

Abstract

Spin valves with a canted pinning field were studied. Magnetoresistance (MR) and planar Hall effect (PHE) in the spin valves were simultaneously measured in fields applied in the film plane at different angles (α) with respect to the easy axis of the free layer. The Boltzmann transport equation was used to simulate MR and PHE curves, and to determine the magnetization orientation of the free layer at different α. Results showed that in the magnetization configuration in which the pinning field was perpendicular to the easy axis of the free layer, there existed two distinct magnetization reversal modes when the applied field angle α was near 90°. The magnetization reversal was an incoherent rotation when α<90°, which gave rise to Barkhausen noises, but was a coherent rotation when α>90°. However, in the configuration in which the angle between the pinning field and the easy axis of the free layer was about 45°, there was only one magnetization reversal mode. The interlayer coupling kept the free layer in a single domain state and constrained the magnetization reversal of the free layer in coherent rotation. Consequently, the MR response exhibited excellent linearity without Barkhauson noise when α was in the range from 75°–105°.