X-ray photoelectron and mossbauer spectroscopy studies of the valence state of transition metal ions in [Co.sub.1-x][Fe.sub.x][Cr.sub.2][O.sub.4] ceramics

The valence state of transition metal ions in the [Co.sub.1-x][Fe.sub.x][Cr.sub.2][O.sub.4] (x = 0.1, 0.2, 0.5) system has been investigated using X-ray photoelectron and Mossbauer spectroscopy. It has been shown that, in this system, there are [Fe.sup.2+] and [Fe.sup.3+] ions. The relative [Fe.sup.3+]/[Fe.sup.2+] contents have been determined by fitting the experimental Fe 2p photoelectron spectra by a superposition of theoretical spectra of the [Fe.sup.2+] and [Fe.sup.3+] ions, as well as using Mossbauer spectroscopy.