Low-temperature heat conduction of γ-irradiated MgO crystals

The effect of γ-irradiation on heat conduction kappa(T) and the spectra of optical and paramagnetic absorption of MgO crystals are studied. For the first time two stages of thermal destruction of optical absorption bands are found and their relation with the process of thermal recovery kappa(T) is established. Contributions to the heat conduction due to both, resonance scattering of phonons on paramagnetic ions Cr2+ (generated in the process of irradiation on account of the change of the impurity valence of Cr3+ and Fe2+) and Rayleigh scattering on radiation (including proper) defects of the MgO lattice are analysed. From the comparison of the calculated data of heat conduction kappa(T) with pertinent experimental data on Cr2+ ion concentration and effectiveness of Rayleigh and anharmonic phonon scattering in MgO crystals are obtained. (author)