X-ray magnetic circular dichroism on Co monodispersive cluster assemblies

X-ray absorption near edge structure (XANES) spectra and x-ray magnetic circular dichroism (XMCD) spectra at the Co K edge have been measured for Co clusters with the mean diameter d = 6-13 nm. The spectral analysis indicates that the fcc phase is predominant for d = 6 nm, while the hcp phase gradually increases with increasing d in agreement with the results of transmission electron microscopy. The 4p orbital moments of clusters tend to decrease in the smaller cluster, but the reduction is small compared with the case of the multilayers, suggesting the importance of surface effects of the Co cluster system.