Time-domain stability of parametric synchronization in a spin-torque nano-oscillator based on a magnetic tunnel junction

Description: 

We report on time-domain stability of the parametric synchronization in a spin-torque nano-oscillator (STNO) based on a magnetic tunnel junction. Parametric synchronization is a phenomena during which the STNO gets locked to an injected signal at twice the eigen frequency of the STNO. Time-domain measurements of the instantaneous frequency of a parametrically synchronized STNO show random short-term unlocking of the STNO signal for low injected radio-frequency (RF) power, which cannot be revealed in time-averaged frequency domain measurements. Macrospin simulations reproduce the experimental results and reveal that the random unlocking during synchronization is driven by thermal fluctuations. We show that by using a high injected RF power, random unlocking of the STNO can be avoided. However, a perfect synchronization characterized by complete suppression of phase noise, so-called phase noise squeezing, can be obtained only at a significantly higher RF power. Our macrospin simulations suggest that a lower temperature and a higher positive ratio of the field-like torque to the spin transfer torque reduce the threshold RF power required for phase noise squeezing under parametric synchronization. The results are important for wireless communication applications of STNOs.

Contact details: 

Dr. P. K. Muduli

Department of Physics

muduli[at]physics.iitd.ac.in