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

Abstract

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.