Spin dynamics evidenced by EPR in Sn1−xMnxO2 nanoparticles annealed at different temperatures

This article reports the effects of the annealing temperature on the structural, morphological and spin dynamic properties of SnO2 samples doped with 0.005 Mn. The samples were annealed at 400, 600, 700 and 800 °C and analyzed by XRD, TEM, XPS and EPR spectroscopy. The XRD spectra show that the average crystallite size increases with the increase of the annealing temperature. The particles size and morphology were characterized by TEM microscopy. The valence bands of Mn were investigated by measuring the XPS spectra of Mn 2p core-level doublet. Regardless of the annealing temperature, the observed EPR spectra are due to (i) Mn2+ ions either interstitially situated on the particle surfaces or isolated ones located substitutionally at Sn sites and (ii) Mn4+ ions which substitute for Sn4+ in SnO2 lattice. The effects of the annealing temperature on the relative fractions of Mn2+ and Mn4+ ions are presented and discussed. In Sn1−xMnxO2 (x = 0.005) sample annealed at 400 °C, a FMR line was identified and attributed to a ferromagnetic phase.

► The mean size of individual nanoparticles was investigated by TEM.
► The annealed temperature influence on Mn2+ and Mn4+ ions content was investigated.
► A ferromagnetic phase was identified by EPR and his origin was explained.