Formation of ferrimagnetic phases during the milling of α-Fe2O3

By ultrafine wet-milling in water of α-Fe2O3of synthetic or natural origin, a surprising increase of magnetism is found. New magnetic phases and their formation conditions were investigated. The magnetic contribution of contaminant resulting from steel ball wear cannot explain this large increase. X-ray diffraction, thermomagnetic analysis and Fe²⁺content confirm the formation of magnetite as the main phase of the dried product. The mechano-chemical reduction of hematite occurs by hydrogen, which results from decomposition of water by abraded ball steel. An important role can be attributed to slight changes of temperature.