Structural and magnetic properties of iron oxides in co-sputtered granular thin films

¹ Laboratoire de Physique de l'État Condensé, UPRESA CNRS 6087, Université du Maine, 72085 Le Mans Cedex 09, France
² Laboratoire d'Optique des Solides, UMR 7601 Université Pierre et Marie Curie, 4 Place Jussieu 75252 Paris Cedex 05, France

Corresponding author: greneche@univ-lemans.fr

Received: 4 August 1999
Revised: 21 December 1999
Accepted: 28 December 1999
Published online: 15 February 2000

Abstract

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.