Observation of injection and pinning of domain walls in magnetic nanowires using photoemission electron microscopy

Photoemission electron microscopy is used to explore the injection and pinning of magnetic domain walls in 250-nm-wide, 20-nm-thick Permalloy nanowires. Domain walls are injected from a micron-sized elliptical nucleation pad at one end of the nanowire. A vortex-like structure is readily nucleated in this pad at low magnetic fields (<15Oe), whereas injection of a domain wall into the nanowire requires significantly larger fields (∼60Oe). Domain walls are pinned in the nanowire at notches patterned along the wire’s edges. The domain walls are observed to have vortex-like structures with chiralities that vary in successive experiments.