Fluorine doping inducing high temperature ferromagnetism in (In1−xFex)2O3

► Fluorine (F) doping in (In1−xFex)2O3 was achieved by the process of a low temperature reaction with polyvinylidene fluoride. ► Ferromagnetism was obtained in the F-doped (In1−xFex)2O3. ► The Curie temperature of ferromagnetism is as high as 675K. ► The ferromagnetism originates from the mixed-valence Fe2+–Fe3+ pairs. ► The ferromagnetism in the F-doped (In1−xFex)2O3 still exists even after high temperature annealing in air. Fluorine (F) doping in (In1−xFex)2O3 was achieved by the process of a low temperature reaction with polyvinylidene fluoride (PVDF). Ferromagnetism with a Curie temperature as high as 675K was obtained in the F-doped (In1−xFex)2O3. It is found that F doping leads to reduction of Fe valence state from Fe3+ to Fe2+. The saturated magnetic moment (Ms) shows a maximum value when the ratio of Fe2+/Fe3+ is 50%, indicating that the mixed-valence Fe2+–Fe3+ pairs play an important role in inducing the ferromagnetism. Interestingly, it is further found that the ferromagnetism in the F-doped (In1−xFex)2O3 still exists even after high temperature annealing in air.