Thermal conductivity of REAl2compounds (RE=rare earth)

Abstract

The temperature dependence of the thermal conductivity lambda (T) of the REAl₂ compounds (RE=Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu) is shown in the range from 4.2K to room temperature. Generally it is assumed that lambda (total thermal conductivity) is given by the sum of two contributions ( lambda = lambda _e+ lambda _g), where lambda _e and lambda _g are the electronic and the lattice thermal conductivities respectively. It could be shown that lambda _g for the REA1₂ compounds is negligible at least for low temperatures (T2 compounds (RE=Y, La, Lu) LaAl₂ shows a considerably different lambda (T) behaviour which the authors have related to an enhanced electron-phonon coupling in this compound. The spin-dependent scattering contribution to the electronic thermal resistivity (W_spd) has been obtained by using Matthiessen's rule (W_e=W_e,0+W_e,ph+W_spd). Experimentally they found that W_spd=DT^-1 for most of the heavy REAl₂ compounds, which is in good agreement with a theoretical calculation of W_spd(T). From both the experiment and the theory they could show that D is proportional to the de Gennes factor. The analysis of the thermal resistivity of CeAl₂ (known as a Kondo lattice system) demonstrates that Delta WT varies as (-ln T) in two temperature regions ( Delta W=W(CeAl₂)-W(YAl₂)). The same behaviour has been observed for rho _spd(T) in CeAl₂.