Domain Walls in Magnetic Wires with Antinotches and Tapering

The propagation of domain walls in magnetic wires is strongly affected by the wire materials, dimensions, and stray fields from adjacent magnetic structures. The wire shape has a major influence on the reliability of the propagation behavior and determines whether the propagation is stochastic or well controlled. We investigate the effect of anti-notches as they act in general as obstacles for a moving domain wall, which has to expand while passing the wider structure. In the special case of current driven domain wall motion the current density (as the main driving force) is also reduced at an antinotch. Depending on the material anti-notches have been shown to exhibit a reduced depinning threshold compared to notch-shaped obstacles. We have used both simulations and experimental work to examine systematically the propagation of domain walls past antinotches to map a reliable regime of operation.

domain walls in magnetic wires with antinotches and tapering

We also found that tapering of the edge of the wire has important effects on domain wall structure and dynamics. Modeling shows that it stabilizes transverse walls, and incrases the current at which Walker Breakdown takes place, allowing higher domain wall velocities. Tapering can also change the anisotropy of the material, which is a thickness dependent effect. For example in Co/Pd multilayers the perpendicular anisotropy is smaller at a tapered edge, giving sites for reverse domain nucleation, whereas in FePt L10 films the anisotropy is higher at the edge.