Investigating Vortex Core Motion Driven by Thermal Gradients

Magnetic vortices can be driven by spin polarized currents. The magnetization dynamics of such motion is described by the extended Landau-Lifshitz-Gilbert equation. In this work, we focus on spin polarized currents created by thermal gradients utilizing the Spin-Seebeck effect. Using full micromagnetic simulations we have studied the effects of different temperature gradients, lateral sample sizes, sample thicknesses, and damping parameters on the resulting vortex motion. Our results show that high temperature gradients are required to excite a measurable vortex core motion in a thin Permalloy sample. To increase the vortex motion, we also discuss the use of pulsed heating, which results in resonantly driven vortex motion. To further analyze our numerical results, we use an extended Thiele equation to analyze the gyroscopic motion of the thermally driven vortices. The good agreement between the full micromagnetics simulations and the semi-analytical solutions of the extended Thiele equation allows us to extend the analytical model to include magnonic effects and random temperature fluctuations.