Micromagnetic Study of Vortex Dynamics Excited by Field Pulses

In ferromagnetic nanostructures, the magnetic vortex is a stable configuration in which the magnetization curls in-plane around a central core. This core, known as the vortex core, has an out-of-plane magnetization, its polarity, which can point either “up” or “down,” while the in-plane circulation, or chirality, can be clockwise or counterclockwise [1-3]. Together, these two degrees of freedom make the vortex state an attractive candidate for information storage, where the polarity can represent a classical bit in spintronic devices.

This research focuses on investigating the controlled switching of vortex polarity through perturbations of the magnetization structure induced by external magnetic field pulses. The reversal process is strongly dependent on the energy delivered by the pulse, which in turn is determined by its amplitude and duration. Micromagnetic simulations based on the Landau–Lifshitz–Gilbert (LLG) equation, implemented in OOMMF and MuMax3, were performed on a Permalloy disk to analyze this behavior.

Preliminary results show that it is possible to change the vortex polarity by controlling the magnetic field pulses. Thus, we observed the processes of creation and annihilation of vortex–antivortex pairs, as well as explored different field pulse shapes. This investigation facilitates the control and manipulation of vortices for spintronic devices.

[1] Q. F. Xiao, R. R. P. Singh, Z. P. Li, D. S. Wang, and W. L. Yang, "Dynamics of vortex core switching in ferromagnetic nanodisks," Appl. Phys. Lett. 89, 262507 (2006).

[2] R. Hertel and C. M. Schneider, "Exchange explosions: magnetization dynamics during vortex-antivortex annihilation," Phys. Rev. Lett. 97, 177202 (2006).

[3] M. Urbánek, L. Flajšman, and M. Horák, "Dynamics and efficiency of magnetic vortex circulation reversal," Phys. Rev. B 91, 094415 (2015).