Impact of magnetoresistance and anisotropy on synchronized Spin Torque Oscillators

Synchronization of pairs of serially connected spin torque oscillators (STO) was studied using Landau-Lifshitz-Gilbert-Slonczewski magnetodynamic simulations. The impact of realistic process variations on STO synchronization was estimated by allowing for different in-plane anisotropy fields (H_k) in the two STOs. We find that the synchronized state is extremely sensitive to STO process variations and can only sustain up to 4% H_k variation. However, the addition of a small time delay dramatically improves the robustness of the synchronization and allows as much as 145% H_k variation in the entire out-of-plane precession regime.