Vortex Polarity Switching by a Spin-Polarized Current

Abstract

The spin-transfer effect is investigated for the vortex state of a magnetic nanodot. A spin current is shown to act similarly to an effective magnetic field perpendicular to the nanodot. Then a vortex with magnetization (polarity) parallel to the current polarization is energetically favorable. Following a simple energy analysis and using direct spin-lattice simulations, we predict the polarity switching of a vortex. For magnetic storage devices, an electric current is more effective to switch the polarity of a vortex in a nanodot than the magnetic field.

Limits for the vortex state spin torque oscillator in magnetic nanopillars: Micromagnetic simulations for a thin free layer

“…In this current range, the moving vortex oscillates with a stationary orbit determined by the current value, I. If the current exceeds I c2 , 21,22 the vortex steady motion state is not stable anymore, presumably because the vortex reaches a critical velocity 9 and reverses its core. Vortex core precession and reversal effects are quite well-known now 9,[20][21][22][24][25][26][27] and have been numerically simulated.…”

“…The particular cases of an in-plane current, [16][17][18] nanopillar magnetization dynamics under the influence of a perpendicular polarizer, [19][20][21][22][23][24][25][26][27][28] a vortexlike polarizer [29][30][31] or nanocontacts [32][33][34] were considered.…”

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

“…However, the rigid approach fails when considering the vortex dynamics under the influence of a strong or fast external force. In particular, it is known that external pumping excites internal modes in vortex dynamics in Heisenberg magnets, whose role is important for understanding the switching phenomena [6,7,8,9,10,11], and the limit cycles in the vortex dynamics [12,13].…”

Understanding eigenfrequency shifts observed in vortex gyrotropic motions in a magnetic nanodot driven by spin-polarized out-of-plane dc current

“…[9][10][11][12][13][14][15][16][17][18][19][20] For instance, the current-driven vortex gyrotropic oscillation [9][10][11][12][13] and vortex core ͑VC͒ M switching [14][15][16][17][18][19][20] in confined magnetic systems have been observed both experimentally [9][10][11]13,14 and numerically. 12,[15][16][17][18][19][20] Despite the several studies conducted on the STT effect on such vortex excitations, quantitative understanding of the Oersted field ͑OH͒ effect of the spinpolarized currents has been lacking, even though this type of field has been reported to make sizable contributions to M reversals 5,21,22 and VC oscillations. 9,10,13 In this letter, we report the observation of sizable shifts in the intrinsic eigenfrequency D = ͑1 / 2 ͒ , of vortex gyrotropic motions in a laterally confined thin-film nanodot.…”