Spin-transfer-induced microwave oscillations in spin valves with ferromagnetic nano-contacts in oxide spacer layer

We observed microwave oscillations induced by spin-transfer torque in spin valves with ferromagnetic nano-contacts in oxide spacer layer near the antiparallel magnetic moment configuration between the free and the reference layers. The frequency of the microwave oscillation ranges from 4.2 to 9.7 GHz and the Q-value of the level peak reaches as high as around 300. We showed that the frequency of the oscillation depends on the applied current and magnetic field, which can be qualitatively explained by considering the response of the domain walls confined in nano-contacts to the applied current and magnetic field. (fast track communication)