An electron back-scattering Mössbauer spectroscopy study of thin magnetite films

Magnetite films of thickness 16–282 Å were prepared by oxidation of thin ⁵⁷Fe films at 220°C in 5 × 10^-3 Torr oxygen and investigated using electron back-scattering Mössbauer spectroscopy. At room temperature the internal hyperfine fields (H_int) due to the A and B site cations in Fe₃O₄ show a systematic decrease with decreasing film thickness. The spectrum from the 16 Å-thick oxide shows collapse of the magnetic patterns to give a superparamagnetic quadrupole split doublet. All spectra recorded at 12.5 K exhibit six broad peaks of a magnetically split pattern with H_int greater than at room temperature but showing little change with oxide thickness.