Young K. Yoo

Room temperature ferromagnetic n-type semiconductor in (In1−xFex)2O3−σ

The thin film synthesis and characterization of room temperature ferromagnetic semiconductor (In1−xFex)2O3−σ are reported. The high thermodynamic solubility, up to 20%, of Fe ions in the In2O3 is demonstrated by a combinatorial phase mapping study where the lattice constant decreases almost linearly as Fe doping concentration increases. Extensive structural, magnetic and magneto-transport including anomalous Hall effect studies on thin film samples consistently point to a source of magnetism within the host lattice rather than from an impurity phase.

Bulk synthesis and high-temperature ferromagnetism of (In1−xFex)2O3−σ with Cu co-doping

The synthesis and magnetic properties of (In1−xFex)2O3−σ bulk ceramics with Cu co-doping are reported. Magnetic Fe ions are found to have high thermodynamic solubility (up to 20%) in the In2O3 host compound. The lattice constant decreases almost linearly as Fe doping concentration increases indicating the incorporation of Fe ions into the host lattice. The samples with high Fe concentration annealed under Ar reduced atmosphere were found to be ferromagnetic, and the Curie temperature is around 750K. The extensive structural and magnetic studies rule out the possibility that the observed magnetism is derived from magnetic impurity phases.

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.