The Oscillator Strength of the Soft Mode in Li₂Ge₇O₁₅

Abstract

The temperature dependences or the soft TO mode and the associated LO mode in Li₂Ge₇O₁₅ have been measured by Raman scattering technique in the ferroelectric phase. The frequency of the LO mode decreases as T_c is approached from below. The LO–TO splitting of the soft mode was observed to be smaller than 1 cm⁻¹. The results are discussed in the relationship with those obtained through measurements of dielectric constant. The oscillator strength for the polar soft mode in the paraelectric phase is expected to be very small.