Remanent States and Magnetization Reversal for Nanopatterned Co Elements

The remanent states and reversal behavior of 10-nm-thick polycrystalline Co elements have been investigated using off-axis electron holography and Lorentz microscopy. Different shapes with dimensions in the range of 100-1200 nm were observed, including rectangles with different size and aspect ratio as well as rings and slotted rings. Virgin states of circular and rectangular elements showed a variety of patterns including centered and off-centered vortices. At remanence, rectangles with rounded edges revealed multiple domains separated by a domain wall running transverse to the longer axis. The magnetization reversal behavior of rectangles with regular edges involved S-shaped and bidomain states, whereas the reversal mechanism for rectangles with rounded edges involved "Y" and "V" shaped domain walls separating the magnetic domains. Reproducible switching was observed when these latter shapes were subjected to repeated field cycles