Increasing the Correlation Time of Spin-Torque Oscillators Synchronized by Magnetostatic Interactions

Synchronization of spin-torque oscillators (STOs) via magnetostatic interactions is investigated. In order for arrays of STOs to be used to carry out computational tasks the STOs should remain phase-locked for as long as possible. The correlation time for two STOs is shown to depend on H{d}{({3}/{2})} , where H{d} is the strength of the magnetostatic interaction between the STOs. For a 1-D array of STOs, introducing an angle between adjacent STOs can reduce the magnetostatic energy and increase the correlation time by an order of magnitude, or more. The increase in correlation time is resilient to moderate distributions of size and position among the STOs.