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Far‐Infrared and Submillimetre Dielectric Response of (NH 4 ) 2 BeF 4
Author(s) -
Petzelt J.,
Volkov A. A.,
Kozlov G. V.
Publication year - 1980
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220990118
Subject(s) - dielectric , infrared spectroscopy , infrared , anomaly (physics) , reflection (computer programming) , absorption (acoustics) , spectroscopy , materials science , far infrared , absorption spectroscopy , phase transition , phason , phase (matter) , analytical chemistry (journal) , condensed matter physics , chemistry , optics , physics , optoelectronics , phonon , organic chemistry , chromatography , quantum mechanics , computer science , composite material , programming language
The far‐infrared spectrum of the complex dielectric constant ε*(ω) of (NH 4 ),BeF 4 single crystals is measured by means of precise transmission spectroscopy (5 to 34 cm −1 region) and reflection spectroscopy (34 to 400 cm −1 region) at 90 and 300 K. The temperature dependence of ε″ (30 cm −1 ) revealed a disorder‐induced absorption in this region, but no other anomaly in the incommensurate phase due to amplitudon or phason absorption, confirming the order‐disorder nature of the incommensurate phase transition.