Preparation and characterization of ilmenite-hematite thin films

Abstract Ilmenite-hematite solid solution (Fe2−xTixO3) is one of the candidates for practical magnetic semiconductors with the high Curie temperature (TC). We have successfully prepared well-crystallized and epitaxial Fe1.4Ti0.6O3 films by using a reactive helicon plasma sputtering technique. The structural characterizations indicated that the films had the order structure ( R 3 ¯ symmetry), where Ti- and Fe-rich layers were stacked alternately along the c-axis, without any secondary phase. The subsequent annealing of the films in vacuum at 700 °C promoted the R 3 ¯ symmetry. Only the films having the good R 3 ¯ symmetry had large ferrimagnetic moments at room temperature. The resistivities of the films clearly showed semiconducting behavior, i.e., logarithmic resistivity showed a monotonous increase with increasing the inverse temperature. The minimum room temperature resistivity of the films was about 10−1 Ω cm. From the Hall effect measurement all films had n-type conduction. The carrier concentration was estimated to be about 1019–1021 cm−3, depending on the annealing conditions.