We numerically investigate effect of the angular dependence of spin-transfer torque (STT) on current-induced precession mode in symmetric spin-valve structures where two ferromagnets are free to move. Two spin-valve structures with NiFe and Co as ferromagnets are studied, which show considerably different angular dependence of STT. We find that the zero-field microwave oscillation occurs in symmetric spin-valve structures. Precession frequency can reach around 10 GHz and decreases with increasing current. In contrast to a spin-valve structure with a single free layer, the blue shift is not observed due to highly nonlinear coupling of two magnetizations. We find that more symmetric angular dependence of STT allows the magnetic excitation at a lower current and provides a more monotonous increase of output power.
Bibliographical noteFunding Information:
This work was supported by the Degree of Research Center (DRC) Program funded by the Korea Research Council of Fundamental Science and Technology (KRCF).
- Diffusive transport
- Microwave oscillation
- Spin transfer torque
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering