Structural and magnetic phenomena in ultrathin C/Co/C stacks prepared by DC magnetron sputtering

We study two C(5 nm)/Co/C(5 nm) multilayer stacks with cobalt layer thicknesses of 4 and 13 nm. Structural analysis of fabricated systems reveals corresponding cobalt layers to be in amorphous (nanocrystalline) and [0001]-textured hcp-phase. The magnetic measurements for both systems agree well with structural data. For the amorphous cobalt layer magnetic data reveal the absence of carbides, high saturation field of 1.6 × 10 4 Oe and vanishing inplane coercive field. We also show that strong inplane anisotropy can be introduced into the amorphous cobalt film by controlling the process parameters of DC-magnetron sputtering. For the textured hcp-cobalt film we have deduced the presence of randomly close-packed (rcp) structure. We assume this defect-rich cobalt hcp-phase to be responsible for the detected elimination of the out-of-plane magnetic anisotropy in the corresponding multilayer sample.