Jpn. J. Appl. Phys. 36 (1997) pp. 3318-3323 |Next Article| |Table of Contents|
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Brillouin Scattering from the Soft Optical Phonon in the Orthorhombic Form of a K 3Co 1-xFex(CN) 6 (x≤ 0.03) Crystal
Department of Basic Sciences, Faculty of Science and Engineering, Ishinomaki-Senshu University,
Shinmito, Minamisakai, Ishinomaki 986-80, Japan
1Department of Physics, Faculty of Science, Tohoku University, Aramaki Aza-Aoba, Aoba-ku, Sendai 980-77, Japan
2Department of Chemistry, Faculty of Science, Saitama University, Shimo-okubo, Urawa 388, Japan
(Received October 23, 1996; accepted for publication January 28, 1997)
The soft optical phonon in the two-layer orthorhombic form of a K3Co1-xFex(CN)6 (x≤0.03) single crystal has been reinvestigated using a (3+3)-pass tandem Fabry-Pérot interferometer around the structural phase transition temperature. The soft phonon response can be well described using the phonon-relaxator coupled model. The soft phonon frequency ω∞/2π obeys the |T-T c±|1/2 law except in the vicinity of T c=82.5 ±0.1 K; (ω∞/2π)2=1.20×103(T-82.1) (GHz2) for T>T c and 4.55×103(83.0-T) (GHz2) for T<T c. The soft phonon-relaxator coupling constant increases linearly above the T c as the temperature decreases and the slope becomes steeper below T c. The relaxation time is longer than 40 ps and independent of temperature above T c, but becomes one order of magnitude shorter below T c. The Fe3+ defects seem to be responsible for these unusual temperature dependences.
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