Electronic transport through domain walls in ferromagnetic nanowires:  Coexistence of adiabatic and nonadiabatic spin dynamics

We study the effect of a domain wall on the electronic transport in ferromagnetic quantum wires. Conduction channels arise due to the transverse confinement. In the presence of a domain wall, spin-up and spin-down electrons in these channels become coupled. For very short domain walls or at high longitudinal kinetic energy, this coupling is weak, leads to very few spin flips, and a perturbative treatment is possible. For very long domain-wall structures, the spin follows adiabatically the local magnetization orientation, suppressing the effect of the domain wall on the total transmission, but reversing the spin of the electrons. In the intermediate regime, we numerically investigate the spin-dependent transport behavior for different shapes of the domain wall. We find that the knowledge of the precise shape of the domain wall is not crucial for determining the qualitative behavior. For realistic quantum wires, electrons with low longitudinal energy are transmitted adiabatically, while the electrons at high longitudinal energy are essentially unaffected by the domain wall. Taking this coexistence of different regimes into account should be important for the description of recent experiments.