Nanoimprint lithography of high-density cobalt dot patterns for fine tuning of dipole interactions

High-density Co dot arrays with a very high filling factor were fabricated by using a trilayer nanoimprint technique. Use of hydrane as the top layer resist gave better dimensional control of the replicted patterns compared to polymethyl(methacrylate) (PMMA) and permitted fine tuning of the size of the patterns by adjusting the etching time in the transfer process. Cobalt dot arrays with different diameters and periods were characterized magnetically and dipolar interactions among the dots were demonstrated as a function of both array period and dot diameter. The magnetization reversal process was observed to occur by nucleation/annihilation of magnetic vortices.