Hybrid Fe3O4-Gd2O3 Nanoparticles Prepared by High-Energy Ball Milling for Dual-Contrast Agent Applications

This work investigates the feasibility of synthesis hybrid x Gd2O3 + (100 − x) Fe3O4 nanoparticles using the scalable method of high-energy ball milling for dual-contrast magnetic resonance imaging applications. Comprehensive studies of the structure, magnetic and functional properties of the hybrid nanoparticles were conducted. It was found that the milling process initiates the transformation of the cubic phase c-Gd2O3 (Ia3¯) into the monoclinic m-Gd2O3 (C2/m). Measurements of the magnetic properties showed that the specific saturation magnetization of the Fe3O4 phase is substantially reduced, which is a characteristic feature of nanoparticles due to phenomena such as surface spin disorder and spin-canting effects. The transmission electron microscopy results confirm the formation of hybrid Fe3O4-Gd2O3 nanostructures and the measured particle sizes show good correlation with the X-ray diffraction results. A comprehensive structure–property relationship study revealed that the obtained hybrid nanoparticles exhibit high r2 values, reaching 160 mM−1s−1 and low r1 values, a characteristic that is determined primarily by the presence of a large fraction of Gd2O3 particles with sizes of ≈30 nm and Fe3O4 crystallites of ≈10 nm.