Origin of ferromagnetism in semiconducting (In{sub 1-x-y}Fe{sub x}Cu{sub y}){sub 2}O{sub 3-{sigma}}

We systematically measure and analyze x-ray absorption fine structure and the anomalous Hall effect of recently discovered room-temperature ferromagnetic semiconductor thin films (In{sub 1-x-y}Fe{sub x}Cu{sub y}){sub 2}O{sub 3-{sigma}}. The x-ray fine structure demonstrates that divalent Fe ions exist in ferromagnetic samples but not in nonmagnetic ones, suggesting a mobile-electron-mediated ferromagnetism. The anomalous Hall behavior is found to be consistent with that of ferromagnets, in which carriers are delocalized, but qualitatively different from that of double-exchange manganites, in which carriers are bound to magnetic ions, confirming that the ferromagnetism in (In{sub 1-x-y}Fe{sub x}Cu{sub y}){sub 2}O{sub 3-{sigma}} is mediated by mobile electrons.