Mutually synchronized 2D spin Hall nano-oscillator arrays with quality factors up to 170,000

Nano-constriction based Spin Hall nano-oscillators (SHNOs) have emerged as an attractive alternative to spin torque nano-oscillators [1,2], as their auto-oscillating mode exhibits substantial spatial expansion in out-of-plane fields [3], propagating spin waves can be generated [4], and long chains of nano-constrictions can be mutually synchronized [5]. Here we demonstrate that it is also possible to synchronize nano-constriction SHNOs in two dimensions. We fabricate 2D square SHNO arrays ranging from 2 x 2 to 10 x 10 constrictions and study their microwave signal properties in out-of-plane fields using both electrical measurements and Brillouin Light Scattering microscopy. We observe robust mutual synchronization in up to 8 x 8 arrays and find that their quality factor, Q = f/Δf, increases in direct proportion to the number of mutually synchronized constrictions, with the largest arrays showing Q = 170,000.

[1] T. Chen et al., Proc. IEEE 104, 1919 (2016)
[2] V. Demidov et al., Appl. Phys. Lett. 105, 172410 (2014)
[3] M. Dvornik, A. A. Awad, and J. Åkerman, Phys. Rev. Appl. 9, 014017 (2018)
[4] H. Fulara et al., Sci. Adv. 5, eaax8467 (2019)
[5] A. A. Awad et al., Nature Physics 13, 292–299 (2017)
[6] M. Zahedinejad et al., Nature Nanotechnology, accepted (2019); arXiv:1812.06350