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Temperature and Frequency Dependence of the Dielectric Constant and Proton NMR near the Structural Phase Transition of Squaric Acid
Author(s) -
Maier H.D.,
Müller D.,
Petersson J.
Publication year - 1978
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.2220890232
Subject(s) - squaric acid , dielectric , dispersion (optics) , proton , phase transition , materials science , dielectric dispersion , phase (matter) , frequency dependence , condensed matter physics , low frequency , constant (computer programming) , nuclear magnetic resonance , chemistry , permittivity , optics , physics , organic chemistry , optoelectronics , quantum mechanics , astronomy , computer science , programming language
Abstract The frequency‐and temperature‐dependent dielectric constant is measured in directions parallel to the molecular layers of squarie acid crystals. There is a monodispersive relaxational dispersion step in the low‐frequency regime Which is ascribed to a thermally activated diffusional motion. The dielectric constant, which is the high‐frequency limit of this dispersion step, is influenced by the 100°C structural phase transition in a characteristic manner. In order to account for the observed behaviour different models are discussed. The measured orientational dependence of the proton NMR spectrum is related to the structural data.