Large amplitude vortex gyration in Permalloy/Bi$_2$Se$_3$-like heterostructures

TL;DR

This paper demonstrates that large amplitude vortex gyration in Permalloy/Bi$_2$Se$_3$ heterostructures can be excited efficiently using microwave currents, leveraging high charge-to-spin conversion ratios, with potential for low-current vortex control.

Contribution

It provides analytical and micromagnetic analysis of vortex excitation via microwave currents in heterostructures with high charge-to-spin conversion, revealing analogies to Landau phase transitions.

Findings

Large amplitude vortex gyration can be excited with lower current densities.

Micromagnetic modeling confirms the dependence on microwave frequency and amplitude.

The vortex dynamics show analogies to Landau phase transition theory.

Abstract

We consider the excitation of large amplitude gyrotropic vortex core precession in a Permalloy nanodisk by the torques originating from the in-plane microwave current flowing along the interface of the Permalloy/Bi$_2$Se$_3$ heterostructures, in which the huge charge-to-spin conversion ratio is observed \cite{Mellnik-2014}. We consider analytically and by micromagnetic modelling the dependence of this excitation on the frequency and magnitude of the microwave current. The analogies of the vortex dynamics and the Landau phase transitions theory is demonstrated. These findings open the possibility to excite gyrotropic vortex motion with the current densities far lower than by any other means.