Effects of Edge Taper on Domain Wall Structure and Current-Driven Walker Breakdown in a Ferromagnetic Thin Film Wire

Domain walls in a ferromagnetic thin film wire with rectangular cross section adopt transverse wall (TW) or vortex wall (VW) geometries depending on the magnetic material and the wire width and thickness. However, experimentally wires can have a trapezoidal cross section if they are made by liftoff using an undercut resist profile. Micromagnetic modeling shows that tapering of the wire not only promotes the formation of a TW over a VW, but also increases the critical current value and the domain wall velocity at which Walker breakdown occurs, providing a potential route to higher speed domain wall devices.