Current-induced domain wall motion in permalloy nanowires with a rectangular cross-section

We performed micromagnetic simulations of the current-induced domain wall motion in permalloy nanowires with rectangular cross-section. In the absence of the nonadiabatic spin-transfer term, a threshold current, J(c) is required to drive the domain wall moving continuously. We find that J(c) is proportional to the maximum cross product of the demagnetization field and magnetization orientation of the domain wall and the domain wall width. With varying both the wire thickness and width, a minimum threshold current in the order of 10(6) A/cm(2) is obtained when the thickness is equivalent to the wire width. With the nonadiabatic spin-transfer term, the calculated domain wall velocity v equals to the adiabatic spin transfer velocity u when the current is far above the Walker limit J(w). Below J(w), nu = beta/alpha u, where beta is the nonadiabatic parameter and a is the damping factor. For different beta, we find the Walker limit can be scaled as J(w) = alpha/vertical bar beta-alpha vertical bar J(c). Our simulations agree well with the one dimensional analytical calculation, suggesting the findings are the general behaviors of the systems in this particular geometry. (C) 2011 American Institute of Physics. [doi:10.1063/1.3658219]