Width dependent auto-oscillating properties of constriction based spin Hall nano-oscillators
Ahmad A. Awad, Afshin Houshang, Mohammad Zahedinejad, Roman Khymyn, Johan Åkerman
Abstract
We study the current tunable microwave signal properties of nano-constriction-based spin Hall nano-oscillators in oblique magnetic fields as a function of the nano-constriction width, w=50−140 nm. The threshold current is found to scale linearly with w, defining a constant threshold current density of Jth= 1.7 × 108 A/cm2. While the current dependence of the microwave frequency shows the same generic nonmonotonic behavior for all w ⩾ 80 nm, the quality of the generated microwave signal improves strongly with w, as the total power increases and the linewidth decreases linearly with w. As a consequence, the peak power for a 140 nm nano-constriction is about an order of magnitude higher than that for an 80 nm nano-constriction. The smallest nano-constriction, w= 50 nm, exhibits a different behavior with a higher power and a worse linewidth, indicating a crossover into a qualitatively different narrow-constriction regime.