New properties of Fe3O4@SnO2 core shell nanoparticles following interface charge/spin transfer

The synthesis and properties of Fe3O4@SnO2 core-shell nanoparticles are reported in the present paper. To form Fe3O4@SnO2 nanocomposites (FeSn-Ox), the magnetite (Fe3O4) nanoparticles were covered with SnO2 semiconductor through the use of the seeding method followed by a thermal treatment. XRD studies reveal that the synthesized composite nanoparticles contain mainly Fe3O4 and SnO2 in different proportions depending on the preparation conditions. The composition of nanoparticles and their core-shell architecture were evidenced by XPS and confirmed by Fourier analysis of HRTEM images. Magnetic studies also indicated that FeSn-Ox samples exhibit superparamagnetic behavior at room temperature. It was found that the SnO2 shell nanocrystals contain ordered magnetic moments formed through a charge/spin transfer process across the interface (carrier-mediated ferromagnetism). The analysis of UV-vis and photoluminescence (PL) spectra of FeSn-Ox composites shows position modifications of SnO2 impurity band gap levels in accordance with the charge/spin transfer between Fe3O4 and SnO2 outer shell.