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 10⁶A/cm² is obtained when the thickness is equivalent to the wire width. With the nonadiabatic spin-transfer term, the calculated domain wall velocity ν equals to the adiabatic spin transfer velocity u when the current is far above the Walker limit J_w. Below J_w,

ν=

β   α

u

, where β is the nonadiabatic parameter and α is the damping factor. For different β, we find the Walker limit can be scaled as

Jw=  α    β-α   Jc

. Our simulations agree well with the one dimensional analytical calculation, suggesting the findings are the general behaviors of the systems in this particular geometry.