On the acoustic nature of a microwave echo in silicate glasses

The results on the magnetic field dependence of the intensity of a microwave echo in silicate glasses containing paramagnetic impurities are used to construct a model of the formation of an echo as a super-position of an acoustic electron spin echo of the system of paramagnetic impurities and a polarization echo of the ensemble of quartz microcrystals present in the glass. Representing microcrystals in the glass as an ensemble of acoustic oscillators makes it possible to explain the anomalous low-temperature specific heat of glasses without invoking the model of localized two-level tunneling centers.