Dynamics of magnetic domain walls in nano wires in the presence of a mesoscopic electric current

Bernhard Kramer

School of Engineering and Science, International University Bremen, Bremen, Germany

Jun-ichiro Ohe, 1. Institut für Theoretische Physik, Universität Hamburg, Jungiusstrasse 9, Germany
Bernhard Kramer, International University Bremen, Campus Ring 1, 28759 Bremen

The dynamics of a single domain wall in a one dimensional magnetic system is studied numerically in the presence of a spin-polarized electrical current in the quantum coherent limit. We find that in addition to the spin torque induced by the current in the adiabatic limit, the displacement of the domain wall is influenced by spin waves that are generated by non-adiabatic contributions. The resulting average domain wall velocity can be much smaller than the one in the adiabatic approximation. Results for the dynamics of the spins in a magnetic domain under the influence of a current embedded in a quasi-one dimensional system are also reported. We find that with sufficiently small spin-polarized currents the magnetic domain can be switched between different polarizations. If the current exceeds a critical value depending on the geometry of the domain, the local spins undergo a transition towards a dynamic disordered state. The phase diagram of the magnetic behavior of the domain under the influence of the current is numerically determined.

Ref.: J.-i. Ohe, and B. Kramer, Phys. Rev. Lett. 96, 027204 (2006)