Current-Driven Domain-Wall Depinning in Pt/CoFe/Pt Nanowires with Perpendicular Magnetic Anisotropy

The spin transfer torque efficiency was determined experimentally by observing the current-driven domainwall depinning of Pt/CoFe/Pt nanowires with perpendicular magnetic anisotropy. The depinning time was exponentially proportional to the applied magnetic field, and was well explained by the Neel-Brown formula. The depinning time and threshold magnetic field were varied considerably by injecting current into the nanowire. The spin transfer torque efficiency was estimated to be $(7.2{\pm}0.9){\times}10^-15Tm^2$/A from the linear dependence of the threshold current density with respect to the applied magnetic field.