Influence of material defects on current-driven vortex domain wall mobility

Abstract

Many future concepts for spintronic devices are based on the current-driven motion of magnetic domain walls through nanowires. Consequently a thorough understanding of the domain wall mobility is required. However, the magnitude of the nonadiabatic component of the spin-transfer torque driving the domain wall is still debated today as various experimental methods give rise to a large range of values for the degree of nonadiabaticity. Strikingly, experiments based on vortex domain wall motion in magnetic nanowires consistently result in lower values compared to other methods. Based on the micromagnetic simulations presented in this contribution we can attribute this discrepancy to the influence of distributed disorder which vastly affects the vortex domain wall mobility, but is most often not taken into account in the models adopted to extract the degree of nonadiabaticity.

Domain walls within domain walls in wide ferromagnetic strips

“…Possible origins for the symmetry breaking leading to incoherent precession of m DW in different parts of the DW could be edge effects, and/or quenched disorder, interacting with the DW [10,[14][15][16][17][18][19][20]; these may include dislocations, precipitates, grain boundaries, thickness fluctuations of the strip, etc. Here we explore the dynamics of extended DWs in wide CoPtCr PMA strips, with a Bloch wall equilibrium structure, using large-scale micromagnetic simulations with and without quenched disorder.…”

Thermal effects on transverse domain wall dynamics in magnetic nanowires

“…In this equation, c depicts the gyromagnetic ratio, a the Gilbert damping constant, b ¼ Pl B =eM s ð1 þ b 2 Þ with P the polarization of the spin-polarized current, e the electron charge, l B the Bohr magneton, b the degree of non-adiabaticity, 14,15 and M s the saturation magnetization. m, the normalized magnetization (with unit length), and H eff , the effective field, are both space and time varying vector fields.…”

Intrinsic nonadiabatic topological torque in magnetic skyrmions and vortices

“…As a matter of fact, vortex walls are nonlocal objects composed of a vortex core and two transverse walls [9][10][11][12], expanding over several exchange lengths in the wire. Because of their spatial extension magnetic vortices are very sensitive to defects and get easily pinned [18][19][20][21]. In contrast, skyrmions are localized objects with a limited expansion from a few tens to one hundred nanometers [8].…”