Irreversible switching of vortex core in Pac-man nanodisks induced by rotating magnetic fields

Vortex has attracted great attention recently due to its potential applications in information storage, nano-oscillators and logic devices. The control of vortex polarity is key to the devices based on vortex. In this paper, an irreversible vortex core (VC) switching in Pac-man disks has been investigated by micromagnetic simulations. The switching process is closely related to the evolution of energy densities and there is a sharp peak in the local exchange energy density when VC switching occurs. Irreversible switching of VC can be realized due to the weak interaction between reversed vortex and rotating magnetic field. In the process of VC reversal, the positive and negative magnetization regions of the gyrofield are separated. Moreover, the switching time of VC decreases monotonously with frequency under rotating magnetic fields. When one direction of the rotating magnetic field is turned off, the difference in switching time is attributed to the different motion behaviors of vortex. This work benefits the potential storage applications in vortex-based spintronic devices.