THERMAL CONDUCTIVITY OF RARE-EARTH-DOPED CAF2 IN MAGNETIC FIELDS

Thermal-conductivity measurements have been taken on nine samples of CaF2 doped with Dy3+, Ho3+, and Ce3+ in the range 0.4 to 4.2 °K and in magnetic fields to 40 kOe. Resonance spin-phonon absorption is clearly discernable for CaF2: 0.001% Dy3+. For higher dopings of Dy3+, nonresonance absorption becomes important. Ho3+ yields more complicated results. Ce3+ conductivity is nearly independent of field. Zero-field conductivities follow T3 behavior over a wide range of dopant concentrations. This is attributed to nonresonant scattering by the paramagnetic impurities with finite zero-field splittings. © 1969 The American Physical Society.