Synchronization of vortex-based spin torque nano-oscillators by magnetostatic coupling

•Vortex-based nanopillar oscillators re synchronized by the dipolar interaction.•There is a range of frequencies where both oscillators will frequency-locked.•There are upper and lower critical currents defining a locking range.

Synchronization of two nanopillar oscillators driven by spin torque and coupled through the magnetic dipolar interaction. The dominant mode in each oscillator is gyrotropic motion of the vortex core in an elliptical orbit about the free layer disk center. The dynamic properties of this mode is investigated by solution the coupled Thiele equations with both nanopillar oscillators having identical dimensions, but with a current mismatch. It is noticed that there is a range in the current difference where the oscillators will be synchronized where the vortex gyrotropic motion will be frequency-locked with the radii of gyrotropic motion equal for both disks. There is, however, a phase shift between the gyrotropic motion with the smaller current disk lagging the higher current disk by a few degrees.