Evidence for magnetic interactions among magnetite nanoparticles dispersed in photoreticulated PEGDA-600 matrix

Magnetite nanoparticles having mean diameter of about 8 nm have been prepared by a thermo-chemical route. Different amounts (5 and 10% wt) of a stable dispersion of magnetite nanoparticles in n-hexane were added to polyethylene glycol diacrylate (PEGDA-600) oligomer containing 2% wt of radicalic photoinitiator. The homogenized mixture was poured on a silica glass substrate and the resulting film was photoreticulated in N₂ atmosphere using a UV lamp. As a result, a polymer-based magnetic nanocomposite was obtained, where the magnetic nanoparticles are dispersed in the diamagnetic matrix, as checked by SEM. Morphology, composition, and size of as-prepared nanoparticles were checked by SEM and X-ray diffraction. The magnetic properties of magnetite nanoparticles prior to and after inclusion in the polymeric matrix have been studied by means of an alternating-gradient magnetometer (T interval: 10–300 K, H_MAX: 18 kOe). FC-ZFC curves were obtained in the same temperature interval. The results show that the nanocomposites cannot be simply described as containing superparamagnetic particles undergoing an anisotropy-driven blocking and that collective magnetic interactions play a non-negligible role. Low-temperature hysteretic properties indicate that the polymeric matrix affects the effective anisotropy of magnetite nanoparticles. Dispersion of magnetite NPs in PEGDA has non-trivial consequences on their magnetic properties.