Shebanova and Lazor made also experiments on fine-grained powder of magnetite. The increase of laser power is producing effects on Raman spectrum attributed to oxidation. "Broadening and a deterioration of bands in the 400-600 cm -1 region, along with the development of a new peak at about 700 cm -1 , indicate the first stage of the oxidation of magnetite … The presence of hematite bands in the spectrum, along with those of maghemite, is explained by the metastability of maghemite with respect to hematite. The Raman spectra collected at higher powers are consistent with pure hematite" .