Microwave excitations associated with a wavy angular dependence of the spin transfer torque: Model and experiments

作者：Boulle O; Cros V^*; Grollier J; Pereira L G; Deranlot C; Petroff F; Faini G; Barnas J; Fert A

来源：Physical Review B, 2008, 77(17): 174403.

DOI：10.1103/PhysRevB.77.174403

The spin transfer torque (STT) can lead to a steady precession of magnetization without any external applied field in magnetic spin valves where the magnetic layers have very different spin diffusion lengths. This effect is associated with a nonstandard dependence of the STT, called "wavy" angular dependence of the STT (WAD-STT), predicted in the frame of diffusive models of spin transfer. In this paper, we present a complete experimental characterization of the magnetization dynamics in the presence of a WAD-STT. The results are compared to the prediction of the magnetization dynamics obtained by single domain magnetic simulations (macrospin approximation). The macrospin simulations reproduce well the main static and dynamical experimental features and suggest that the dynamical excitations experimentally observed are associated with a large angle out-of-plane precession mode. The present work validates the diffusive models of the spin transfer and underlines the role of the spin accumulation and the spin relaxation effects on the STT.

• 出版日期2008-5