We study the current tunable microwave signal properties of nano-constriction based spin Hall nano-oscillators (SHNOs) 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 non-monotonic behavior for all w⩾ 80 nm, the quality of the generated microwave signal improves strongly with w, showing a linear w dependence for both the total power and the linewidth. As a consequence, the peak power for a 140 nm nano-constriction is about an order of magnitude higher than that of a 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.
Cite
@article{arxiv.2003.07178,
title = {Width dependent auto-oscillating properties of constriction based spin Hall nano-oscillators},
author = {Ahmad A. Awad and Afshin Houshang and Mohammad Zahedinejad and Roman Khymyn and Johan Åkerman},
journal= {arXiv preprint arXiv:2003.07178},
year = {2020}
}