Deposition of Co nano-particles in a CoO/Al2O3 matrix by magnetron sputtering

We have explored the use of sequential sputtering as an alternative way of growing Co clusters inside an antiferromagnetic matrix of CoO. The samples are composed of 10 bi- or tri-layers and have been deposited by direct magnetron sputtering of Co, CoO and Al2O3 targets. Transmission electron microscopy and impedance spectroscopy measurements show that the direct deposition of Co over CoO does not favor the Volmer-Weber tridimensional mode in the tested range of Co nominal thicknesses. In the samples where an Al2O3 layer is formed prior to the Co deposition, Co aggregates of nano-size are formed and retained when the empty space is filled by CoO. Some preliminary results of the magnetization as a function of temperature are presented and discussed