Mechanochemical synthesis and characterization of gallium oxide-hematite magnetic nanostructures

Mixed oxide nanoparticle systems recently attracted considerable interest, due to their potential applications in sensing, catalysis, and flexible electronics. In this study, we synthesized gallium oxide–hematite nanostructures using mechanochemical activation by high energy ball milling at three molar concentrations and ball milling times of 0, 2, 4, 8, and 12 hours. The prepared systems were characterized by transmission Mossbauer spectroscopy and analyzed by least squares fitting using Lorentzian lineshapes. For 0-hours, the spectrum was fitted using a sextet with hyperfine magnetic field of 51.9 T, characteristic to hematite. Spectra of the milled samples were analyzed using additional sextets according to the model of local atomic environment. These sextets had lower hyperfine magnetic field values due to substitutions of non-magnetic gallium ions at the iron sites. The subspectra could be assigned to gallium-doped hematite. A quadrupole-split doublet with a quadrupole splitting of about 0.7 mm/s was needed to account for the superparamagnetic gallium iron perovskite (gallium orthoferrite) phase. Our results demonstrate that Mossbauer spectroscopy is a powerful technique for the identification of crystalline phases and inequivalent lattice sites in the system.