RAMAN-STUDY OF CRITICAL FLUCTUATIONS NEAR THE PHASE-TRANSITION IN FERROELECTRIC LI2GE7O15

The anomalous behavior of the soft mode in the Raman spectra of the Li 2Ge7O15 polar phase has been found to be in good agreement with renorm alization group (RG) theoretical results in the short-range scaling re gion 7 < T-c - T < 43 K. The values and the temperature dependence of the dimensionless critical susceptibility, the order parameter correla tion lengths along the orthorhombic axes and the bare soft phonon damp ing constant have been obtained along with the scaling indexes nu = 0. 631 +/- 0.002, gamma = 1.23 +/- 0.03 and the Ginzburg parameter Gi app roximate to 0.41 from a least-squares fit of the RG Formula to the Ram an data.