Effective demagnetizing tensor incorporating finite width effect for magnetic nanowire design in racetrack devices

Abstract

Structural engineering is a promising approach to enhance the performance of racetrack devices in term of power consumption for domain wall dynamics and shift errors via the control of the in-plane shape anisotropy in magnetic nanowires. Because the in-plane shape anisotropy is determined by the nanowire width, it is essential to incorporate the width effect into the demagnetizing tensor to design racetrack devices through a structural approach; however, a quantitative evaluation of the width effect on the demagnetizing tensor is still lacking. In this work, we have derived the formula for the effective demagnetizing tensor in nanowires with finite width. We also analytically revealed that the special width, at which intrinsic pining potential vanishes, is proportional to the domain wall width. The derived formulas were in good agreement with the two-dimensional micromagnetic simulation results at various nanowire widths, demonstrating their validity. Our results provide a guideline for designing racetrack devices with low power consumption and minimal shift errors via structural engineering.