Current-induced domain wall motion in Ni80Fe20 nanowires with low depinning fields

Abstract

In this paper, we report on domain wall (DW) motion induced by current pulses at variable temperature in 900 nm wide and 25 nm thick Ni80Fe20 wires with low pinning fields. By using Ar ion milling to pattern our wires rather than the conventional lift-off technique, a depinning field as low as ∼2–3 Oe at room temperature is obtained. Comparison with previous results acquired on similar wires with much higher pinning shows that the critical current density scales with the depinning field, leading to a critical current density of ∼2.5 × 1011 A m−2 at 250 K. Moreover, when a current pulse with a current density larger than the critical current density is injected, the DW is not necessarily depinned but it can undergo a modification of its spin structure which hinders current-induced DW motion. Hence, reliable propagation of the DW requires an accurate adjustment of the pulsed current density.