Exchange bias of Co/CoO multilayers deposited on nanosphere array

The [Co/CoO] 5 multilayer nanocap arrays are fabricated on the colloidal sphere arrays which are prepared on the Si substrate by the self-assembly technology. Compared to bilayer film, the H EB of multilayer film is larger than that of the bilayer film. The increase of H EB for multilayer should be ascribed to the interface increase between FM and AFM layers. In the multilayer film structure, H EB of the nanocap array is bigger than that of the flat film, which is attributed to the decrease of FM layer thickness, the decrease of grain size, and the increase of structural defects caused by curved substrate. And the typical step is observed in flat, and the step is reduced significantly in the nanocap array due to the enhancement of interfacial coupling between neighbor FM layers. For the [Co/CoO] 5 multilayer nanocap array, H EB increases first, and then decreases when CoO sublayer thickness changes. When CoO sublayer thickness is 15 nm, H EB reaches its maximum. This result may be related to the topography of nanostructure multilayer on curved substrate.