Raman Scattering in Langasite-Family Crystals

Resumo

Raman scattering spectra have been investigated in La₃Ga₅SiO₁₄ langasite crystals with Cr and Fe impurities and La₃Ga_5.25Ta_0.25Si_0.5O₁₄ crystalline solid solution. It is shown that all spectra contain a low-frequency peak near 110 cm^–1. The La₃Ga_5.25Ta_0.25Si_0.5O₁₄ crystal exhibits high-frequency peaks in the range from 1000 to 2000 cm^–1, which are much stronger than the low-frequency peaks. The intensities of the Raman peaks recorded in the La₃Ga₅SiO₁₄ crystal are close in the entire spectral range. The differences in the spectra of the ideal single crystal and solid solutions can be explained by the manifestation of additional modes in the solid solutions.