Phonon spectroscopy of the low-energy excitations in the solid solutions of yttrium–rare-earth metal–aluminum garnets

Abstract

The transport characteristics of thermal-frequency phonons and the specific heat of a series of single crystals of yttrium–rare-earth metal–aluminum garnet solid solutions are studied at the helium temperatures. It is found that the existence of low-energy levels of various origins, which are responsible for an increase in the specific heat, retards phonon transport by one–three orders of magnitude. The temperature dependences of specific heat and the kinetic characteristics of phonons have a similar character.