Switching behavior of nanoscale Co ferromagnetic elements using off-axis electron holography

The switching behavior of 20-nm-thick nanoscale Co ferromagnets has been investigated using the technique of off-axis electron holography. Elements having elliptical, dumbbell, ring and “Pacman” shapes were fabricated on electron-transparent silicon nitride membranes using standard electron-beam lithography and lift-off techniques. Ellipses generally showed linear switching but interactions between closely spaced elements occasionally caused inconsistent switching. Dumbbells, rings and disk-like Pacman shapes developed intermediate vortex states during switching, which caused broad switching fields. Ring-like Pacman shapes had negligible fringing field and switched very rapidly without the formation of any vortex state.