THE TEMPERATURE DEPENDENCE OF THE RAMAN BANDWIDTHS FOR THE HARD MODES OF THE AMMONIUM HALIDES CLOSE TO PHASE TRANSITIONS
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Date
2000
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Ohio State University
Abstract
This study gives the temperature dependence of the Raman bandwidths for the $\nu_{5} (174 cm^{-1})$ mode of $NH_{4}Cl$ and for the $\nu_{5} (117 cm^{-1})$ mode of $NH_{4}Br$. We analyze our observed Raman bandwidths of those phonon modes according to the soft-hard mode coupled model close to the phase transitions in these crystals. Our analyses give that the values of the critical exponent for the Raman bandwidths are $\beta = 0.13$ for the $\nu_{5} (174 cm^{-1})$ mode of $NH_{4}Cl (T_{c} = 241.3K)$ and for the $\nu_{5} (177 cm^{-1})$ mode of $NH_{4}Br (T_{c} = 234K)$ in the first order phase region of these crystalline systems.
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Author Institution: Department of Physics, Istanbul Technical University