Domain wall mobility, stability and Walker breakdown in magnetic nanowiresA. Mougin1, M. Cormier1, J. P. Adam1, P. J. Metaxas1, 2 and J. Ferré1
1 Laboratoire de Physique des Solides, Université Paris-Sud, CNRS, UMR 8502, F-91405 Orsay Cedex, France
2 School of Physics, MO13, University of Western Australia - 35 Stirling Highway, Crawley, WA 6009, Australia
received 6 March 2007; accepted in final form 26 April 2007; published June 2007
published online 31 May 2007
We present an analytical calculation of the velocity of a single domain wall in a magnetic structure with reduced thickness and/or lateral dimension under the combined action of an external applied magnetic field and an electrical current. As for the case of field-induced domain wall propagation in thick films, two motion regimes with different mobilities are obtained, below and far above the so-called Walker field. Additionally, for the case of current induced motion, a Walker-like current density threshold is defined. The threshold field and current density, stating the wall's internal structure stability, differ from those in thick films; both are reduced by the same geometrical demagnetising factor which accounts for the confinement. This points out the fact that the velocity dependence over an extended field/current range and the knowledge of the Walker breakdown are mandatory to draw conclusions about the phenomenological Gilbert damping parameter tuning the magnetisation dynamics.
75.60.Ch - Domain walls and domain structure .
75.75.+a - Magnetic properties of nanostructures .
72.25.-b - Spin polarized transport .
© Europhysics Letters Association 2007