Due to their nonlinear properties, spin transfer nano-oscillators can easily adapt their frequency to external stimuli. This makes them interesting model systems to study the effects of synchronization and brings some opportunities to improve their microwave characteristics in view of their applications in information and communication technologies and/or to design innovative computing architectures. So far, mutual synchronization of spin transfer nano-oscillators through propagating spinwaves and exchange coupling in a common magnetic layer has been demonstrated. Here we show that the dipolar interaction is also an efficient mechanism to synchronize neighbouring oscillators. We experimentally study a pair of vortex-based spin transfer nano-oscillators, in which mutual synchronization can be achieved despite a significant frequency mismatch between oscillators. Importantly, the coupling efficiency is controlled by the magnetic configuration of the vortices, as confirmed by an analytical model and micromagnetic simulations highlighting the physics at play in the synchronization process.

Phase locking dynamics of dipolarly coupled vortices excited by spin-polarized current in two identical nanopillars is studied as a function of the interpillar distance L. Numerical study and analytical model have proved the remarkable efficiency of magneto-static interaction to achieve phase locking. Investigating the dynamics in the transient regime towards phase locking, we extract the evolution of the locking time τ , the coupling strength µ and the interaction energy W . Finally, we compare this coupling energy with the one obtained by simple model.

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We report on a theoretical study of the magnetodipolar coupling and synchronization between two vortex-based spin-torque nano-oscillators (STVOs). In this work we study the dependence of the coupling efficiency on the relative magnetization parameters of the vortices in the system. This study is performed in order to propose an optimized configuration of the vortices for synchronizing STVOs. For this purpose, we combine micromagnetic simulations, the Thiele equation approach, and the analytical macrodipole approximation model to identify the optimized configuration for achieving phase-locking between neighboring oscillators. Notably, we compare vortices configurations with parallel (P) core polarities and with opposite (AP) core polarities. We demonstrate that the AP core configuration exhibits a coupling strength about three times higher than in the P core configuration.