Angular Dependent Auto-Oscillations by Spin-Transfer and Spin-Orbit Torques in Three-Terminal Magnetic Tunnel Junctions

Spintronic oscillators are promising candidates for neuromorphic computing due to their true miniaturization, non-linearity and synchronization properties. However, spin torque nano-oscillators are excited by current-induced spin-transfer torque which may cause high power consumption and reliability problems. Spin Hall nano-oscillators can realize higher energy efficiency, while their relatively low power emission limits their further applications. Here, we demonstrate three-terminal magnetic tunnel junction based spin torque nano-oscillators excited by the combination of spin-transfer and spin-orbit torques under different angle configurations. Thanks to the large spin Hall angle (-0.278) of W, the ratio between threshold current density of spin-transfer and spin-orbit torques for auto-oscillations can reach 0.6, indicating their high energy efficiency. Furthermore, we observe that the ratio has a sine function dependence on the angle between the spin-polarization directions of spin-transfer and spin-orbit torques. Our work could benefit the development of high-efficiency spintronic oscillators and their large network designs.