ROLE OF DECAY PROCESSES IN THE PROPAGATION OF SLIGHTLY NONEQUILIBRIUMTHERMAL-PULSE PHONONS IN YALO3LU CRYSTALS

Data on the propagation of slightly nonequilibrium phonons, Delta T mu ch less than T-b (T-b is the cryostat bath temperature) in Y0.9Lu0.1Al O3 crystals with effective elastic scattering by rare-earth metal atom s are analyzed. The experimental results are interpreted on the basis of the ''quasidiffusion'' model, where three-phonon inelastic decay pr ocesses play a decisive role in the phonon kinetics. Monte Carlo calcu lations with these processes taken into account yield good quantitativ e agreement with the experimental data. (C) 1997 American Institute of Physics.