Magnetic field-induced ferromagnetism in iron oxide microspheres

A magnetic field of 12 T was applied during the annealing of amorphous α-Fe2O3 microspheres. The authors demonstrate that magnetic field processing leads to the formation of γ-Fe2O3 phases in the microspheres, and the field-treated microspheres exhibit typical room-temperature ferromagnetic behavior, whereas non-field-heated sample presents paramagnetism. The improvement in magnetic properties is considered to be a result of magnetic field-induced transformation from α-Fe2O3 to γ-Fe2O3.