Resonance scattering of phonons on paramagnetic ions (high temperatures, high ion concentration)

A theory of resonance phonon scattering on paramagnetic levels of rare-earth ions for medium and high temperature ranges is developed. The case of a high concentration of paramagnetic ions is considered. Temperature dependences have been obtained for the (-Δx)sub(res) quantity, i.e., for the decrease of heat conduction because of resonance scattering on paramagnetic ions. For an ordered arrangement of paramagnetic ions in the crystal lattice this quantity is roughly proportional to Tsup(1/2) and for a disordered arrangement to T-1. In the temperature range from 80 to 400 deg K the heat conduction of Pr2Te3, Pr3Te4, La2Te3, and La3Te4 has been measured. For praseodymium compounds the absolute value of (-Δx)sub(res) and its temperature dependence have been determined. A comparison of theory with experiment has shown a satisfactory agreement. Attention is called to the fact that paramagnetic ions, being the principal component of Pr3Te4 and Pr2Te3 compounds, scatter phonons as impurity atoms. This leads one to believe that, no matter how pure these compounds may be, they will always contain an additional ''impurity heat resistance''