Vortex domain wall formation in Permalloy nanowires with constriction based pinning

The potential for magnetic domain walls (DWs) within Permalloy nanowires to be used as non-volatile data storage has prompted a surge in research to meet the fabrication and operational challenges of these DW devices. Utilising a spin polarised current, it has been proposed that transporting vortex DWs is preferential over transverse DWs to accommodate lower currents. It is also believed that pinning sites - either a constriction or a doped area - must be used to allow reliable and controlled operation. In this paper, we present a number of micro-magnetic simulations which investigate the qualitative pinning potential of some constriction-based pinning sites and the implications for reliably forming vortex DWs in tight confinement within Permalloy nanowires.