N. Randrianantoandro et al., Structural and magnetic properties of iron oxides in co-sputtered granularthin films, EPJ-APPL PH, 9(2), 2000, pp. 125-130
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 Fe-57
Mossbauer spectrometry as a function of iron concentration. A common exper
imental feature reveals that a percolation-like threshold occurs at around
23-25% atomic Fe. Below such a critical value, the co-sputtering process fa
vours the presence of ultrafine amorphous oxide grains with sizes lower tha
n 10 nm embedded in a vanadium oxide matrix. Above, one clearly observes th
e presence of fine grains (sizes comprised between 10-100 nm) composed of e
ither hematite or maghemite phases dispersed in the same matrix, the set di
splaying a magnetic order at room temperature.