Interaction of the TO-phonon with the Acoustic Phonons near the Phase Transition Temperature in Pb1-xGexTe

• Published in: Journal of the Physical Society of Japan Vol. 47; no. 2; pp. 539 - 546
• Main Authors: Sugai, Shunji, Murase, Kazuo, Tsuchihira, Terutoshi, Kawamura, Hajimu
• Format: Journal Article
• Language: English
• Published: Tokyo The Physical Society of Japan 01-01-1979
• ISSN: 0031-9015; 1347-4073
• DOI: 10.1143/jpsj.47.539

The phase transition in Pb1-xGexTe with x=0.03∼0.1 was studied by Raman scattering and ultrasonic velocity measurements. Below Tc the frequency of the A1-mode is 1.99×1023(Tc-T) rad2/sec2 and the E-mode 5.32×1023(Tc-T) rad2/sec2 for x=0.05. The ultrasonic velocity shows a step-like behaviors at Tc. Just above Tc the normal elastic moduli are C11=11.0×1011, C12=0.02×1011 and C44=1.35×1011 in dyn/cm2. The steps are δC11=1.52×1011, δC12=-0.20×1011 and δC44=0.26×1011 in dyn/cm2. The parameters of the free energy expansion were calculated by using the above results together with the data of the shear strain. The order parameter, the spontaneous strain and the TO-phonon frequency above Tc which were estimated from thus obtained parameters are consistent with the results experimentally obtained satisfactorily.