Current-induced spin torque on a domain wall in a magnetic nanowire

Abstract

We develop a theory applicable in the regime, where the wavelength of spin up and down electrons, Af j , is smaller than the DW width L (smooth DW). This regime is appropriate for strongly doped magnetic semiconductors and metallic ferromagnets. We develop an approach related to a weak (adiabatic) perturbation arising after a local transformation to the uniform magnetization. In the limit of L > A|,| we find an exponentially small reflection and spin-flip transition amplitudes. The theory is useful in the regime, where the DW width is not so large, and the perturbation corrections to the wave functions are quite essential. We calculate the current-induced spin density and the spin torque acting locally on the magnetic moments within the DW. The spatially-distributed torque acts as a force pushing the DW in one direction as a response to the external current, and also as an internal force, which can distort the static ordering of magnetic moments in the DW.