Structural investigations of Co/ZrO2 discontinuous multilayers by x-ray absorption fine structure spectroscopy

X-ray absorption spectroscopy (XAS) is used to probe the evolution of the local order around the cobalt atoms in Co/ZrO2 discontinuous multilayers as a function of the nominal Co layer thickness. A decrease of the mean number of Co nearest neighbours around Co atoms is observed as the Co layer nominal thickness decreases. XAS analysis is made according to a justified simple model based on two possible Co sites referred to as metallic (cobalt coordinated) and oxide (oxygen coordinated) sites. XAS results are in agreement with the results obtained by other structural characterizations using transmission electron microscopy and by magnetic and transport measurements showing the morphological evolution of the Co layers from the discontinuous state (multilayer of Co nanoparticles embedded in the oxide) to the continuous one by increasing the Co nominal thickness.