Intrinsic or Interface Clustering-Induced Ferromagnetism in Fe-Doped In₂O₃-Diluted Magnetic Semiconductors

Five percent Fe-doped In₂O₃ films were deposited using a pulsed laser deposition system. X-ray diffraction and transmission electron microscopy analysis show that the films deposited under oxygen partial pressures of 10^-3 and 10^-5 Torr are uniform without clusters or secondary phases. However, the film deposited under 10^-7 Torr has a Fe-rich phase at the interface. Magnetic measurements demonstrate that the magnetization of the films increases with decreasing oxygen partial pressure. Muon spin relaxation (μSR) analysis indicates that the volume fractions of the ferromagnetic phases in PO₂ = 10^-3, 10^-5, and 10^-7 Torr-deposited samples are 23, 49, and 68%, respectively, suggesting that clusters or secondary phases may not be the origin of the ferromagnetism and that the ferromagnetism is not carrier-mediated. We propose that the formation of magnetic bound polarons is the origin of the ferromagnetism. In addition, both μSR and polarized neutron scattering demonstrate that the Fe-rich phase at the interface has a lower magnetization compared to the uniformly distributed phases.