JApplPhys_107_073910.pdf 278 KB
Noami, K. Graduate School of Natural Science and Technology, Okayama University
Muraoka, Y. Graduate School of Natural Science and Technology, Okayama University Kaken ID researchmap
Wakita, T. Faculty of Science, Research Laboratory for Surface Science, Okayama University
Hirai, M. Graduate School of Natural Science and Technology, Okayama University
Kato, Y. Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8
Muro, T. Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8
Tamenori, Y. Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8
A hollandite-type K(x)Ti(8)O(16) polycrystalline sample has been prepared and studied by magnetization, resistivity and x-ray photoelectron spectroscopy (XPS). Room temperature ferromagnetic behavior is observed in the magnetic hysteresis measurement. The sample shows a semiconductive temperature dependence in the resistivity measurement. Analysis of the Ti 2p(3/2) core-level XPS spectrum indicates that the titanium ions have a mixed valence of Ti(4+) and Ti(3+). In addition, the valence band spectrum reveals that the 3d electrons tend to localize on Ti(3+) ions in the hollandite-type TiO(2) lattice. Also, analysis of the valence band spectrum shows that the prepared sample is a wide-gap oxide with a band gap of 3.6 eV. These results indicate that the present hollandite-type K(x)Ti(8)O(16) sample can be classified as a TiO(2)-based wide-gap semiconductor with Curie temperature above room temperature. Room temperature ferromagnetism (RTFM) decreases in the sample prepared under a strong reducing gas atmosphere, accompanied with the decrease in the resistivity. The results imply that the localized 3d electrons are responsible for the RTFM of the K(x)Ti(8)O(16) sample.
Journal of Applied Physics
American Institute of Physics.
© 2010 American Institute of Physics.
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