In the Figure (in cm -1 ). The magnetite is contaminated with laser-independent hematite (experimental conditions with 0.4 mW of 632.817 nm laser line). The spectra of bulk and contaminated magnetite show the magnetite band at 662 cm -1 . "The low-power laser irradiation did not produce any significant variation of hematite/magnetite ratio with time. In contrast, the signal of hematite induced with double the laser power … was progressively growing over that of magnetite. … With 1.6 mW and above, the increase of the hematite signal was almost instantaneous and was accompanied by a disappearance of the magnetite band at 662 cm -1 . The resulting hematite bands were broader and shifted to lower frequencies" . In the Figure by Chourpa and coworkers, we can find the peaks of the Raman spectra of hematite generated by laser power of 0.8 mW and 1.6 mW. Chourpa and coworkers "aimed to prepare superparamagnetic nanoparticles free of antiferromagnetic hematite." They "did not detect any laser-independent hematite in the samples of synthetically prepared nanoparticles. Compared to the bulk oxide, the nanoparticles appeared generally somewhat more resistant to hematite formation upon laser heating: they resisted laser powers of more than 0.4 mW during 1 hour without any spectral change". The researchers also note that, besides the laser power, an exposure to oxygen "is essential for the formation of hematite." Chourpa and coworkers suggest also that the observed "laser-stimulated hematite was formed from pre-initialised oxidation sites (domains rich in oxygen and hematite germs)".