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Magnetic properties of amorphous Ge 1− x Mn x thin films were investigated. The thin films were grown at 373 K on (100) Si wafers by using a thermal evaporator. Growth rate was ∼35 nm/min and average film thickness was around 500 nm. The electrical resistivities of Ge 1− x Mn x thin films are 5.0×10 −4 ∼100 Ω cm at room temperature and decrease with increasing Mn concentration. Low temperature magnetization characteristics and magnetic hysteresis loops measured at various temperatures show that the amorphous Ge 1− x Mn x thin films are ferromagnetic but the ferromagnetic magnetizations are changing gradually into paramagnetic as increasing temperature. Curie temperature and saturation magnetization vary with Mn concentration. Curie temperature of the deposited films is 80–160 K, and saturation magnetization is 35–100 emu/cc at 5 K. Hall effect measurement at room temperature shows the amorphous Ge 1− x Mn x thin films have p-type carrier and hole densities are in the range from 7×10 17 to 2×10 22 cm −3 .

We report on the growth of cubic spinel ZnCo2O4 thin films by reactive magnetron sputtering and bipolarity of their conduction type by tuning of oxygen partial pressure ratio in the sputtering gas mixture. Crystal structure of zinc cobalt oxide films sputtered in an oxygen partial pressure ratio of 90% was found to change from wurtzite Zn1−xCoxO to spinel ZnCo2O4 with an increase of the sputtering power ratio between the Co and Zn metal targets, DCo/DZn, from 0.1 to 2.2. For a fixed DCo/DZn of 2.0 yielding single-phase spinel ZnCo2O4 films, the conduction type was found to be dependent on the oxygen partial pressure ratio: n-type and p-type for the oxygen partial pressure ratio below ∼70% and above ∼85%, respectively. The electron and hole concentrations for the ZnCo2O4 films at 300 K were as high as 1.37×1020 and 2.81×1020 cm−3, respectively, with a mobility of more than 0.2 cm2/V s and a conductivity of more than 1.8 S cm−1.

We report on the structural, magnetic, and magnetotransport characteristics of Cr-doped indium tin oxide (ITO) films grown on SiO 2 /Si substrates by pulsed laser deposition. Structural analysis clearly indicates that homogeneous films of bixbyite structure are grown without any detectable formation of secondary phases up to 20 mol% Cr doping. The carrier concentration is found to decrease with Cr ion addition, displaying a change in the conduction type from n-type to p-type around 15 mol% Cr doping. Room temperature ferromagnetism is observed, with saturation magnetization of ∼0.7 emu/cm 3 , remnant magnetization of ∼0.2 emu/cm 3 and coercive field of ∼30 Oe for 5 mol% Cr-doped ITO. Magnetotransport measurements reveal the unique feature of diluted magnetic semiconductors, in particular, an anomalous Hall effect governed by electron doping, which indicates the intrinsic nature of ferromagnetism in Cr-doped ITO. These results suggest that Cr-doped ITO could be promising for semiconductor spin electronics devices.