Current-induced domain wall motion: Domain wall velocity fluctuations

The spin transfer torque generated by a spin polarized current can generate the domain wall (DW) motion in a magnetic nanowire. We examine fluctuations of a DW velocity induced by uncontrolled edge roughness and defects. In the weak pinning regime (regime I), the fluctuation is small. In the intermediate pinning regime (regime II), the DW velocity fluctuates significantly as the density of pinning centers changes. Moreover the threshold current density for the finite density of pinning centers is found to be noticeably larger than the threshold current density for the escape from a single pinning center. Finally, in the strong pinning regime (regime III), the DW velocity fluctuates as the density of pinning centers changes. But the enhancement of the threshold current density does not occur. Thus the fluctuations of the DW velocity are different in the three pinning regimes. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3125522]open111212sciescopu