In Owens and Orosz, 2006, we can find a study about the "effect of nanosizing on the Raman spectra … of the hematite phase of Fe2O3 produced by laser decomposition of Fe3O4 nanoparticles". In the Figure of their article, we can see analyzed the Raman spectra for bulk and nanoparticles of Fe3O4 recorded at room temperature. "No frequency shifts or broadening of the Raman lines are observed in the nanoparticles compared to the bulk material". In particular, the Raman spectra were obtained with a 632 nm 20 mW laser, with density filter D=4. Owens and Orosz concluded that a "9 nm nanosizing is not affecting the vibrational frequencies in the Fe3O4 nanoparticle" (see also references therein).