Granular Fe-V2O5 thin films with different iron concentrations prepared by
means of radiofrequency magnetron co-sputtering technique were investigated by
means of X-ray diffraction, Transmission Electron Microscopy and
57Fe Mössbauer spectrometry as a function of iron concentration. A common
experimental feature reveals that a percolation-like threshold occurs at around
23−25% atomic Fe. Below such a critical value, the co-sputtering process
favours the presence of ultrafine amorphous oxide grains with sizes lower than
10 nm embedded in a vanadium oxide matrix. Above, one clearly observes the
presence of fine grains (sizes comprised between 10−100 nm) composed of either
hematite or maghemite phases dispersed in the same matrix, the set displaying a
magnetic order at room temperature.