Light scattering studies on structural phase transitions

1979 ◽  
Vol 32 (1) ◽  
pp. 95-101 ◽  
Author(s):  
Terutaro Nakamura ◽  
Yasunori Tominaga ◽  
Masayuki Udagawa ◽  
Seiji Kojima ◽  
Masaaki Takashige

Light scattering spectroscopy has played a crucial role in the study of numerous phase transitions and critical phenomena. In the case of structural phase transitions in crystalline solids, high resolution Raman and Brillouin scattering experiments have provided detailed information on the ‘soft modes’, the highly temperature-dependent lattice vibrations whose frequencies fall towards zero at the transition temperature. The condensation of the soft modes precipitates the spontaneous symmetry breaking which inevitably accompanies these transitions. Ferroelectrics comprise a particular class of crystals exhibiting structural phase transitions which have been investigated extensively by light scattering techniques. In addition to numerous soft mode studies, other subtle aspects of these transitions have been investigated by light scattering, including mode interactions and central peaks. In this presentation, the fundamental aspects of structural phase transitions and their relation to light scattering will be reviewed. A number of light scattering studies of ferroelectric crystals spanning the past decade will be summarized and used to illustrate the current level of understanding of these phenomena.


2014 ◽  
Vol 46 (1) ◽  
pp. 161-166 ◽  
Author(s):  
E. A. Popova ◽  
V. N. Yakovenchuk ◽  
S. G. Lushnikov ◽  
S. V. Krivovichev

1980 ◽  
pp. 95-101
Author(s):  
Terutaro Nakamura ◽  
Yasunori Tominaga ◽  
Masayuki Udagawa ◽  
Seiji Kojima ◽  
Masaaki Takashige

1995 ◽  
Vol 09 (28n29) ◽  
pp. 1817-1838 ◽  
Author(s):  
W. SCHRANZ ◽  
D. HAVLIK ◽  
M. FALLY

The study of dynamical properties of crystals near structural phase transitions is still of great importance. Especially the interest on ultralow-frequency dynamics, i.e. the so called “Central-Peak question” was renewed nowadays through some recent work on the observation of Entropy Fluctuations in macroscopic susceptibilities. This so called Heat-Diffusion Central Peak was previously found in scattering experiments, and the corresponding theory was originally formulated for scattering experiments. In this work we present an overview on previous light scattering measurements of Entropy Fluctuations and very recent results concerning the observation of a Heat-Diffusion Central Peak in macroscopic properties at ultralow frequencies, which provide a new insight into the “old” Central Peak problem. The crossover functions from isothermal to adiabatic behaviour are calculated for the macroscopic susceptibilities.


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