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Applied Physics Letters / Volume 92 / Issue 2 / MAGNETISM AND SUPERCONDUCTIVITY
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Appl. Phys. Lett. 92, 022509 (2008); http://dx.doi.org/10.1063/1.2807274 (3 pages)

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

Sang-Koog Kim, Ki-Suk Lee, Young-Sang Yu, and Youn-Seok Choi

Research Center for Spin Dynamics and Spin-Wave Devices, and Nanospintronics Laboratory, Department of Materials Science and Engineering, College of Engineering, Seoul National University, Seoul 151-744, Republic of Korea

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(Received 24 September 2007; accepted 19 October 2007; published online 16 January 2008)

The authors investigated the technological utility of counterclockwise (CCW) and clockwise (CW) circular-rotating fields (HCCW and HCW) and spin-polarized currents with an angular frequency ωH close to the vortex eigenfrequency ωD, for the reliable, low-power, and selective switching of the bistate magnetization (M) orientations of a vortex core (VC) in an array of soft magnetic nanoelements. CCW and CW circular gyrotropic motions in response to HCCW and HCW, respectively, show remarkably contrasting resonant behaviors, (i.e., extremely large-amplitude resonance versus small-amplitude nonresonance), depending on the M orientation of a given VC. Owing to this asymmetric resonance characteristics, the HCCW (HCW) with ωH ∼ ωD can be used to effectively switch only the up (down) core to its downward (upward) M orientation, selectively, by sufficiently low field ( ∼ 10 Oe) and current density ( ∼ 107 A/cm2). This work provides a reliable, low power, effective means of information storage, information recording, and information readout in vortex-based random access memory, simply called VRAM.

© 2008 American Institute of Physics

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KEYWORDS and PACS

Keywords

current density, magnetic core stores, magnetic recording, magnetic switching, magnetisation, nanostructured materials, Permalloy, random-access storage, soft magnetic materials, spin polarised transport

PACS

  • 85.70.Li

    Other magnetic recording and storage devices (including tapes, disks, and drums)

  • 84.30.Sk

    Pulse and digital circuits

ARTICLE DATA

Digital Object Identifier
http://dx.doi.org/10.1063/1.2807274

PUBLICATION DATA

ISSN

0003-6951 (print)  
1077-3118 (online)

Publisher

$abstract.society.value is a Member of CrossRef American Institute of Physics

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  24. In Ref. 13, such asymmetric VC switching behavior in response to HCCW and HCW was reported only in a high frequency range (~10  GHz) above omegaD.

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Figures (click on thumbnails to view enlargements)

FIG.1
Left column: Geometry and dimensions of the model Py nanodisk, and M distributions of vortex states with (a) up- and (b) down-core orientations, with the CCW rotation of in-plane Ms around the VC. The color and height display the local Ms and their out-of-plane components, respectively. The middle and right columns display the VC trajectories of the vortex gyrotropic motions during relaxation (H0 = 0) from a shift of each VC from its initial center position, and during the vortex motion from its initial center position under Hlin(t) with H0 = 10 Oe and νH at νD = 300 MHz, respectively. The red and blue colors denote the VC trajectories of the up- and down-core orientations, respectively.

FIG.1 Download High Resolution Image (.zip file) | Export Figure to PowerPoint

FIG.2
Illustrations of Hlin (Ilin) in (a), of HCCW (ICCW) in (b), and of HCW (ICW) in (c), rotating with ωH(I) in the film plane. The right column shows the time variation of the magnitude of the field or current components along the x and y axes. The sum of HCCW (ICCW) and HCW (ICW) with equal ωH(I) and H0 (j0) leads to Hlin (Ilin) with the same ωH (I). The superposition of the orthogonal circular fields results in a linear oscillating field, such that (HCCW+HCW)/2 = H0 sin (ωHt)math = Hlin. According to the phase difference between HCCW (ICCW) and HCW (ICW), the direction of the linear field is determined.

FIG.2 Download High Resolution Image (.zip file) | Export Figure to PowerPoint

FIG.3
(a) VC trajectories of gyrotropic motions of a VC driven by Hlin, HCCW, and HCW for different values of νH as noted. The red and blue colors of the trajectories indicate the motions of the initial up-core orientation and of the reversed VC after the VC switching, respectively. (b) Perspective snapshot images of the temporal evolution of VC reversals at the indicated times.

FIG.3 Download High Resolution Image (.zip file) | Export Figure to PowerPoint

FIG.4
All of the data are presented in the same way as those in Fig. 3, except for the application of Ilin, ICCW, and ICW with a current density of j0 = 2×107 A/cm2.

FIG.4 Download High Resolution Image (.zip file) | Export Figure to PowerPoint



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