Thermal Conductivity of FeCl2and CdCl2

An explanation is provided for the thermal-conductivity results of antiferromagnetic Fe${\mathrm{Cl}}_2$ ($T_N=23.5\mathrm{}°$K) in the temperature range 3-80 °K in terms of the phonon-induced electronic excitations among the trigonal crystal and exchange-field-split energy levels of the ${\mathrm{Fe}}^{2+}$ ions in the crystalline lattice of Fe${\mathrm{Cl}}_2$. The phonon scattering is described by a relaxation term which has a resonant character. The boundary, point-defect, and the umklapp scattering processes are basic to both Fe${\mathrm{Cl}}_2$ and Cd${\mathrm{Cl}}_2$. In nonmagnetic Cd${\mathrm{Cl}}_2$, they are, moreover, found sufficient to account for the experimental results.