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    ABSTRACT: The dielectric properties of TEA-CoCl2 Br2 nanocrystals incorporated into the polymethylmethacrylate matrix within the frequency range of 3 × 105 –2.6 × 109 Hz in the temperature region of 90–300 K were investigated. The considerable difference in the dielectric spectra of the nanocomposite compared to those of the bulk crystal and the pure polymer matrix was observed. The dielectric dispersion of the composite material reveals a resonance type (resonance frequency was found to be near 1.3 GHz) and may be qualitatively explained as the result of piezoelectric resonance on the nanocrystals. The model interpretation of this phenomenon based on the forced-dumped oscillator is presented.
    Journal of Physics Condensed Matter 09/2008; 20:365215. · 2.22 Impact Factor
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    ABSTRACT: We have studied lattice dynamic properties of SrTiO3 thin films from 5 to 300 K using metal-oxide bilayer Raman scattering. First-order zone-center optical phonons, symmetry forbidden in single crystals, have been observed in the thin films, indicating strain-induced lowering of symmetry. The asymmetric line shape of the TO2 phonon is interpreted as evidence for micropolar regions in the thin films, likely due to oxygen vacancies. The optical phonon lines and the asymmetry persist up to room temperature.
    Physical Review Letters 05/1999; 82(22):4500-4503. · 7.73 Impact Factor
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    ABSTRACT: Semiconducting oxides offer the potential for exploring and understanding spin-based functionality in a semiconducting host material. Theoretical predictions suggest that carrier-mediated ferromagnetism should be favored for p-type material. Cu2O is a p-type, direct wide bandgap oxide semiconductor that may hold interest in exploring spin behavior. In this paper, the properties of Mn-doped Cu2O are described. Activities focused on understanding Mn incorporation during thin-film synthesis, as well as magnetic characterization. The epitaxial films were grown by pulsed-laser deposition. X-ray diffraction was used to determine film crystallinity and to address the formation of secondary phases. SQUID magnetometry was employed to characterize the magnetic properties. Ferromagnetism is observed in selected Mn-doped Cu2O films, but appears to be associated with Mn3O4 secondary phases. In phase-pure Mn-doped Cu2O films, no evidence for ferromagnetism is observed.
    Solid-State Electronics 12/2003; · 1.51 Impact Factor