Ultra-low-current Spin Hall Nano-oscillators

We report on the magnetodynamic properties and the magnetization auto-oscillations of ultra-low current 20 nm width nano-constriction spin Hall nano-oscillators (SHNOs) fabricated on different substrates and seed layers. Combining an optimized W
88
Ta
12
alloy, low damping CoFeB, and a moderate perpendicular magnetic anisotropy, we push the threshold current down to 35 µA in the best devices. The best overall magnetodynamic properties and lowest threshold currents are obtained when using a 3 nm thick AlOx seed layer in between the high-resistance Si substrate and the W
88
Ta
12
layer.