Reduction of critical current density for domain wall motion in U-shaped magnetic patterns

Abstract

The critical current density required for current-induced domain wall motion (Jc) was reduced by decreasing the magnetization (Ms) of the free layer film of a U-shaped pattern for a domain wall motion memory. The Ms was decreased by adding the nonmagnetic elements Ta and Cu to NiFe films. The Jc of the U-shaped patterns with NiFe–Ta and –Cu decreased as the proportion of Ta and Cu in the NiFe increased. The relations between Ms and Jc were examined and it was found that Jc decreased monotonically from 1.2×1012to0.8×1012A∕m2 as Ms decreased from 1.0to0.6T regardless of what other materials were used. It is considered that the decrease in Ms caused a decrease in the hard axis anisotropy of the pattern, and the Jc decreased as predicted by a one-dimensional model.