Thermal Conductivity and Phonon Scattering by Magnetic Impurities in CdTe

Abstract

Crystals of CdTe containing 1 mole% of Mn, Fe, or ZnTe have been grown from the melt. The segregation coefficients of these impurities and of Co can be understood in terms of differences in the covalent, tetrahedral radii of the various metal atoms. The thermal conductivity, $K$, of these crystals and of pure CdTe has been measured from 3 to 300°K. A table of $K$ values for pure CdTe is given; its $K=0.075\mathrm{}$ W/cm deg at 300°K. The heat transport in pure CdTe is due to phonons, and is limited by phonon scattering by crystal boundaries, isotopes, and other phonons. The local lattice distortions, which are nearly the same for Mn, Fe, and Zn, produce an additional nonmagnetic phonon scattering in the doped crystals. There is also a magnetic scattering, particularly pronounced for the Fe with a $3d^6$ configuration, caused by phonon assisted transitions between various low lying energy levels of the $d$-shell electrons. The nature and spacing of these levels can be predicted by crystal field theory, and there is qualitative agreement between this theory and the experimental results.