Enhanced exchange bias of isolated Co/CoO nanocaps

We demonstrated the fabrication of the isolated magnetic Co/CoO nanocap array by oxidating the single Co layer which was deposited onto the two dimensional polystyrene sphere array. Compared to the continuous film and thicker nanocap structure, HE and HC of the 15 nm Co/CoO isolated cap array were enhanced significantly and were about 4 times as those of the corresponding continuous film, which was ascribed to the formation of the isolated magnetic single domain state due to the magnetic limit around the cap brim after the oxidation treatment. When the beads of the different sizes were used as the substrate, HE increased when the bead size decreased, which was ascribed to the increase of the localized uncompensated CoO spins.