Mössbauer study of the high-temperature phase of Co-substituted magnetites, ${\mathrm{Co}}_{\mathit{x}}$${\mathrm{Fe}}_{3\mathrm{-}\mathit{x}}$${\mathrm{O}}_4$. II. x≥0.1

Transmission Mössbauer spectra at variable temperatures between 80 and 860 K have been collected for Co-substituted magnetities, ${\mathrm{Co}}_{\mathit{x}}$ ${\mathrm{Fe}}_{3\mathrm{-}\mathit{x}}$ ${\mathrm{O}}_4$, with x=0.1, 0.2, and 0.4, and at two selected temperatures with the absorber in a longitudinal external magnetic field of 55 kOe. It is concluded that the interpretation of the spectra based on an earlier reported structural model leads to inconsistent results. An adequate and consistent description was obtained using a superposition of two model-independent hyperfine-field distributions, one arising from the tetrahedral (A) iron species, the second one from the octahedral (B) irons. The evaluated distributions clearly reveal the presence of two distinct B-site components, reflecting the existence of two different electronic states for the B-site irons at temperatures not exceeding ≊650 K. The appearance of two B sites is quantitatively explained on the basis of structural considerations.