SIZE QUANTIZATION OF ACOUSTIC PHONONS IN MICROCRYSTALS SURROUNDED BY AN ELASTIC MATRIX

In analyzing the effect of an elastic glassy matrix on the acoustic vibrations of microcrystals we discovered and confirmed by means of low-frequency Raman scattering that new surface vibrations appear when microcrystals are embedded in a matrix, These vibrations, which are due to the appearance of a restoring force during the rotation of the microcrystals, participate in the low-frequency Raman scattering observed in a number of studies [Phys, Rev. B 47, 1237 (1993); Phys. Rev. B 44, 6243 (1991); JETP Lett, 47, 298 (1988); JETP Lett. 48, 678 (1988)]. It is shown that the effect of the matrix cannot be ignored, even in the case where the Lame constants and the density of the microcrystal are substantially different from those of the matrix. (C) 1995 American Institute of Physics.