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Raman Spectra of [N(CH 3 ) 4 ] 2 ZnCl 4 Single Crystals. III. Activation of Acoustic Phonons in Raman Spectra of the Commensurately Modulated Phases
Author(s) -
Torgashev V. I.,
Yuzyuk Yu. I.,
Rabkin L. M.,
Durnev Yu. I.
Publication year - 1991
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.2221670233
Subject(s) - phonon , raman spectroscopy , raman scattering , spectral line , atmospheric temperature range , crystal (programming language) , lattice (music) , crystal structure , condensed matter physics , materials science , molecular physics , crystallography , physics , chemistry , optics , astronomy , meteorology , computer science , acoustics , programming language
Low‐frequency ( v < 50 cm −1 ) polarized Raman spectra of TMATC‐Zn crystals are studied in the temperature range between 300 and 100 K that covers the range in which the structural phase transitions of this compound occur. The appearance of lines with frequencies below 17 cm −1 is observed in commensurately modulated low‐symmetry phases. These lines correspond to the phonons of transverse acoustic branches in the Γ–Σ–X direction of the normal phase which transfer to the zone center as a result of the unit cell multiplication. A sharp drop in the relaxational contribution to the scattering spectrum is found for frequencies below 20 cm −1 in phases V and VI which is thought to be associated with ordering processes in the crystal lattice.