Impact of Mn²⁺-Si⁴⁺ co-substitution on the electronic structure of Zn_0.3Mn_0.7Fe₂O₄ ferrites studied by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) has been employed to explore the electronic structure of Zn_0.3Mn_0.7+xSi_xFe_2-2xO₄ (x = 0.0–0.3) ferrite series. The Si2p XPS spectra insinuated the presence of Si ions in the +4 valence state. The elemental Si⁰ and suboxide SiO_x are present in the system, the former showing an increase and the latter a decrease in atomic percentage upon Mn–Si substitution. It is also inferred that a fraction of Si⁰ might be residing at the grain boundaries; however, more studies are required to substantiate this. The Fe2p XPS spectra stipulate that ferrous and ferric ions co-occur in the system. The ferrous ions occupy the octahedral sites while the ferric ions dwell on both the octahedral and the tetrahedral sites. The O1s spectra indicate a remarkable increase in the oxygen defects with increasing Mn–Si substitution (x). The Mn2p XPS data indicate that the Mn⁺² states show an overall increasing tendency with increasing Mn–Si concentration. Also, the Mn⁺⁴/Mn⁺³ ratio shows an increment with an increase in Mn–Si substitution.