Spin-current-induced magnetization reversal in magnetic nanowires with constrictions

Abstract

We have performed experiments on current-induced domain-wall motion ͑CIDWM͒ in the case of the domain walls ͑DW͒ trapped within the nanoscale constrictions in patterned NiFe structures. Direct observation of current-induced magnetization reversal was achieved and critical current densities j c were measured in the presence of easy-axis magnetic fields. The direction of CIDWM was found to be along the direction of the electron motion in absence of an applied magnetic field and in the direction of the field when in the presence of even relatively weak fields. Data for the field dependence of j c for both uniform and fast rising pulses suggest that the current, regardless of polarity, assists in the depinning of the DW. Only for the dc case does the data strongly reveal the influence of the electron pressure in promoting or hindering DW motion.

Current Induced Domain‐wall Motion in Magnetic Nanowires

“…We have observed this wall structure using magnetic force microscopy (MFM) imaging in permalloy nanowires more than 20 nm thick. Florez, Krafft and Gomez (2005) have reported similar structures in permalloy wires, 40 nm thick.…”

“…In most of these experiments, the DW is first pinned at either a defect (Thomas et al, 2006;Laufenberg et al, 2006b;Grollier et al, 2004;Lim et al, 2004), or a notch (Florez, Krafft and Gomez, 2005;Hayashi et al, 2006b;Klaui et al, 2005c) or at a cross (Ravelosona et al, 2005). In one report , a quite different experimental method was used: the propagation field along a nanowire is measured while dc currents of both polarities are applied.…”

“…Current-driven DW changes can take place below the critical value or depinning. For example, in the work of Florez, Krafft and Gomez (2005), it was observed that the wall structure was modified even though the DW was still trapped within the notched pinning site. We have also observed this behavior, both using MFM and AMR experiments.…”

Micromagnetic simulation of current-driven domain wall propagation

“…1(a), together with the magnetization distributions along the x-direction. The exact position of the wall is fixed by a notch which pins the domain wall [10,11]. If the wire is not intentionally notched then the position of the wall, an always-present surface 'bump' pins wall in a real structure.…”

Magnetoresistance and domain wall motion in horseshoe Ni80Fe20 wires

“…The results are investigated using the anisotropic magnetoresistance (AMR) effect and micromagnetic simulation. Recently, the studies indicated that the presence of even weak magnetic fields can dramatically boost the speed of the domain wall motion [13]. Here, we report current induced domain wall study in a single layer ferromagnetic horseshoe structure.…”