Maximizing Zero-Field-Cooled Exchange Bias in Crystallized Co@CoO Nanocluster Assembled Thin Film by Varying Film Thickness

In this paper, crystallized core-shell Co@CoO nanocluster assembled thin films with different thicknesses were prepared by magnetron sputtering. A large zero-field-cooled exchange bias (ZEB) around 1280 Oe was obtained in the Co-CoO film with a thickness of 18 nm at 10 K. This phenomenon is mainly due to the formation of oriented Co@CoO core-shell nanoclusters (Co along the easy magnetization axis) in the amorphous Co-CoO matrix, thus exhibiting remnant magnetization, which is responsible for the ZEB. Moreover, the ZEB effect can be tuned by the varying film thickness. When the film thickness is decreased or increased, ZEB becomes weak, even vanishes. This indicates that we can select the desired value of ZEB via a simple control of the film thickness, which will benefit the applications of these thin films in the magnetic industry.