Current Modulation of Nanoconstriction Spin-Hall Nano-Oscillators

Abstract

A single nanoconstriction spin-Hall nano-oscillator (NC-SHNO) in out-of-plane fields is presented as a nonlinear amplitude and frequency modulator operated by radio-frequency (RF) current modulation. The current modulation was carried out in different NC-SHNO nonlinearity regimes corresponding to negative, zero, and positive values of df/dI in order to investigate the device response to an 80 MHz modulating current. Our study shows that current modulation of SHNOs can be quantitatively predicted by a nonlinear frequency and amplitude modulation (NFAM) model using the values of df/dI and d <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> f/dI <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> extracted from the free-running frequency f versus current I profile. The NFAM model reproduces the asymmetric sideband amplitude as well as the red and blue shift of the frequency in excellent agreement with the experimental results. The ability to predict the modulation process is a necessary benchmark in designing SHNO modulators for future integrated microwave circuits.