Laboratoire des Colloides, Verres et Nanomatériaux (LCVN), UMR CNRS 5587, University of Montpellier II, 34095 Montpellier, France.
Phys Rev Lett. 2010 Jul 2;105(1):017601. doi: 10.1103/PhysRevLett.105.017601. Epub 2010 Jun 29.
Hyper-Raman scattering experiments suggest that a splitting of the lowest F{1u}-symmetry mode of PbMg{1/3}Nb{2/3}O{3} crystal occurs in a wide temperature range around its Burns temperature T{d}≈630 K. The upper-frequency component, earlier investigated by inelastic neutron scattering experiments above T{d}, appears to be underdamped even hundred of degrees below T{d}. The lower-frequency component, known below T{d} from far-IR spectroscopy, actually becomes underdamped above T{d}. This suggests that the lower-frequency mode is the "primary" polar soft mode of PbMg{1/3}Nb{2/3}O{3}, responsible for the Curie-Weiss behavior of its dielectric permittivity above T{d}.
超拉曼散射实验表明，在其居里温度 T{d}≈630K 左右的宽温度范围内，PbMg{1/3}Nb{2/3}O{3}晶体的最低 F{1u}-对称模发生分裂。在上文提到的 T{d}以上的非弹性中子散射实验中，较早地研究了上频分量，即使在 T{d}以下数百摄氏度，它似乎也处于欠阻尼状态。在 T{d}以下，远红外光谱可知低频分量，而实际上在 T{d}以上，低频分量也会变得欠阻尼。这表明低频模式是 PbMg{1/3}Nb{2/3}O{3}的“主要”极性软模，负责其介电常数在 T{d}以上的居里-外斯行为。
