Controlled vortex core switching in a magnetic nanodisk by a rotating field

Abstract

The control of the vortex state magnetic nanoparticle by ultrafast magnetic fields is studied theoretically. Using the micromagnetic simulations for the Permalloy nanodisk we demonstrate that the vortex core magnetization can be irreversible switched by the alternating field, rotating in the disk plane, with the frequency about 10 GHz and intensity about 20 mT. We propose an analytical picture of such phenomena involving the creation and annihilation of vortex-antivortex pairs and calculate the phase diagram of the fields parameters leading to the switching.

Polarization Selective Magnetic Vortex Dynamics and Core Reversal in Rotating Magnetic Fields

“…8,9,15 In this letter, we report on the experimental observation of the vortex core dynamics due to in-plane rotating magnetic fields. 500x500x50 nm 3 square Permalloy elements with a magnetic vortex configuration were excited with an in-plane rotating magnetic field B(t)=(B 0 cos(ωt),B 0 sin(ωt),0)) at a frequency |ω/(2π)| close to the frequency of the gyrotropic eigenmode, and were investigated by time-resolved magnetic X-ray microscopy (see Figure 1 and the Methods section).…”

X-ray imaging of the dynamic magnetic vortex core deformation

“…At the very centre of the vortex, a small, stable core exists where the magnetization points either up or down 1,2 . The discovery of an easy core reversal mechanism 3 did not only open the possibility of using such systems as magnetic memories, but also initiated the fundamental investigation of the core switching mechanism itself [4][5][6][7][8][9][10][11][12][13][14][15] . Theoretical modelling predicted that the reversal is mediated by the creation and annihilation of a vortex-antivortex pair 3,4,16 , but experimental support has been lacking until now.…”

Reliable low-power control of ultrafast vortex-core switching with the selectivity in an array of vortex states by in-plane circular-rotational magnetic fields and spin-polarized currents

“…24 Figure 3͑b͒ shows the temporal evolution of the VC switching at the indicated times, representing the underlying mechanism of how the VC reversal takes place in tens of picosecond scale or longer. 6,[9][10][11][12][13]17 For the down-core orientation, only the H CW with H 0 =10 Oe at H = D allows the VC to switch to its reversed M orientation.…”