Universal criterion and phase diagram for switching a magnetic vortex core in soft magnetic nanodots.
The universal criterion for ultrafast vortex-core switching between the up- and down-core bistates in soft magnetic nanodots is investigated by micromagnetic simulations along with vortex-core switching that occurs whenever the velocity of vortex-core motion reaches its critical velocity, upsilon cri = (1.66 +/- 0.18) gamma mean square root of Aex (e.g., upsilon cri = 330 +/- 37 m/s for Permalloy), with the exchange stiffness Aex and the gyromagnetic ratio gamma. On the basis of the universality of upsilon cri, phase diagrams for the vortex-core switching event and switching time with respect to both the amplitude and frequency of a circularly rotating magnetic field are calculated.
Lee
Ki-Suk
KS
Research Center for Spin Dynamics and Spin-Wave Devices, and Nanospinics Laboratory, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744, Republic of Korea.
Kim
Sang-Koog
SK
Yu
Young-Sang
YS
Choi
Youn-Seok
YS
Guslienko
Konstantin Yu
KY
Jung
Hyunsung
H
Fischer
Peter
P