| Nanocrystalline particles composed of ZnO doped with a different content of Fe2O3 (in the range 50-95 wt. %) were prepared by the wet chemistry method. According to the XRD analysis, the samples with 95%, 90%, 80% of iron oxide contained γ-Fe2O3 and ZnFe2O4 phases, while other samples contained ZnFe2O4 and ZnO phases. The mean crystalline size of ZnFe2O4 varied from 8 nm to 30 nm. A magnetic resonance study performed with an electron paramagnetic resonance spectrometer was carried out at room temperature for the obtained samples. A very intense magnetic resonance line with asymmetry depending on the iron oxide concentration was recorded for all samples. For samples containing less than 60% Fe2O3 the resonance line is centred at g=2.005(2) and its integrated intensity increases with the ferrite content, reaching a maximum for a sample with a 70% content of iron oxide. For samples with more than 70% of Fe2O3 the g-factor and the integrated intensity of the resonance signal strongly depend on the ratio of iron in form of γ-Fe2O3 to that in form of ZnFe2O4, decreasing with that ratio. The magnetic resonance study has shown that the resonance line originates from isolated iron(III) ions in zinc ferrite in case of a small iron oxide content and from γ-Fe2O3 magnetic nanoparticles (ferromagnetic resonance lines) for higher concentrations. |
full paper (pdf, 186 Kb)