Single ion scattering contributions to the thermal conductivity of   LiHoF_4 and LiY_{96%}Ho_{4%}F_4
  We have performed extensive zero-field thermal conductivity measurements on single crystal samples of \LiHoF and \LiYHoF below $2.3 K$. By comparing these data to a single ion scattering model, we have shown that the thermal conductivity of \LiYHoF is dominated by simple single-ion scattering while that of \LiHoF shows additional contributions, possibly associated with collective spin excitations. No entirely satisfactory model, however, is available to explain the thermal conductivity of the ferromagnet. 
James Nikkel and Brett Ellman