The dynamics of vertically coupled vortices excited by current with tilted spin polarization

Abstract

Vertically coupled magnetic vortices with potential applications in data storage and processing have attracted great interests in the past two decades. A nonlinear device with short-term memory and controllable activation states is also demanded for neuromorphic computing. In this paper, we investigate the dynamics of vertically coupled vortices with different magnetic configuration excited by a charge current with tilted spin polarization through micromagnetic simulations. It is found that the critical current for the gyration of coupled vortices with parallel polarity is one order larger than that with antiparallel polarity. The eigen-frequency of coupled vortices with parallel polarity is much lower than that with antiparallel polarity. With increasing the inter-disk spacer thickness, the gyration amplitude of vortex with antiparallel polarity becomes smaller. Furthermore, a switching phase diagram study shows that the relative polarity of coupled disks can be manipulated by passing sequential pulse currents. Those results indicate that in a coupled vortex system, the excitation states can be manipulated by controlling the relative polarity (through the applying of currents) and the spacer thickness between them. Our findings provide a device which is more similar to the neurons in human’s brain and being potentially used in spintronic neuromorphic computing.