Room temperature ferromagnetic behavior in the hollandite-type titanium oxide

K. Noami, Y. Muraoka, T. Wakita, M. Hirai, Y. Kato, T. Muro, Y. Tamenori, T. Yokoya

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Abstract

A hollandite-type Kx Ti8 O16 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 2 p3/2 core-level XPS spectrum indicates that the titanium ions have a mixed valence of Ti4+ and Ti3+. In addition, the valence band spectrum reveals that the 3d electrons tend to localize on Ti3+ ions in the hollandite-type TiO2 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 Kx Ti8 O16 sample can be classified as a TiO2 -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 Ti8 O16 sample.

Original languageEnglish
Article number073910
JournalJournal of Applied Physics
Volume107
Issue number7
DOIs
Publication statusPublished - Apr 1 2010

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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