Digitale Medien
Springer
The European physical journal
97 (1995), S. 133-138
ISSN:
1434-6036
Schlagwort(e):
62.20.D
;
78.30
;
64.70.K
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Physik
Notizen:
Abstract Investigations of polarized Raman spectra of orthorhombic betaine fumarate crystals revealed the existence of two low-frequency optic modes which soften slightly on approaching the ferroelastic transition temperatureT c ≈194 K. The eigenvectors of these modes withB 1g -andB 2g -symmetry, respectively, are coupled bilinearly to strains of corresponding symmetries leading to renormalized elastic moduli. It is shown that these couplings account quantitatively for the temperature dependences of the modulic 55andc 66and eventually lead to a ferroelastic transition and a spontaneous shear straine 5s .By optical and dielectric measurements it is confirmed that the transition is of second order and follows a classical Landau behaviour with a critical exponent of the order parameter of 0.5 within experimental error.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01317597
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