Thermal-annealing effects on the structural and magnetic properties of 10% Fe-doped SnO2 nanoparticles synthetized by a polymer precursor method

• Thermal annealing effects in the 10% Fe-doped SnO2 nanoparticles have been studied.
• XRD data analysis shows the formation of the rutile-type structure.
• Raman measurements show the formation of small amount of α-Fe2O3 after the annealing.
• Paramagnetic and magnetically ordered phases were determined after the annealing.
• Spin clusters likely at the particle surface have been formed after the annealing.

In this work, we present the experimental results of Sn0.9Fe0.1O2 nanoparticles synthesized by a polymer precursor method. Studies were performed in the as-prepared (AP) and thermally-annealed (TA) samples. The X-ray diffraction (XRD) data analysis carried out using the Rietveld refinement method shows the formation of only the rutile-type structure in the AP sample and this phase remains stable for the TA sample. Additionally, the mean crystallite size shows an increase from ~4 nm to ~17 nm after the annealing and a clear reduction of the residual strain has also been determined. Micro-Raman spectroscopy measurements show the formation of an iron oxide phase (likely α-Fe2O3) after the thermal treatment. Magnetic measurements show a paramagnetic behavior for the AP sample and the coexistence of a weak ferromagnetism and paramagnetism for the TA sample. The magnetically-ordered contribution of the TA sample has been assigned to the formation of the hematite phase. DC and AC magnetic features of the TA sample are consistent with a cluster-glass behavior which seems to be related to the magnetic disorder of spins located at the particle surface. Those spins clusters seem to be formed due to the diffusion of iron ions from the core of the particle to the surface caused by the annealing process.