Abstract
The intermetallic compounds of Yb with In and Cu (YbIn1−xCu4+x) and Yb with In, Ag, and Cu (YbIn1−yAg y Cu4) exhibit interesting magnetic and transport properties. Of the compounds of Yb with In and Cu the compound with x=0, namely YbInCu4, has attracted particular attention, because—while being a Curie–Weiss paramagnet—it undergoes a first-order isostructural phase transition at T v =approx. 40 to 80 K and atmospheric pressure. Below T v the ytterbium in this compound is in a mixed-valence state and the compound as a whole is sometimes called a light heavy-fermion system. Above T v , the compound is known as a Curie–Weiss paramagnet of localized magnetic moments and, below T v , a Pauli paramagnet in a nonmagnetic Fermi-liquid state. In the present paper the results of measurements of the thermal conductivity of polycrystalline samples, YbIn1−xCu4+x with x=0,0.015, 0.095, and 0.17 and YbIn1−yAg y Cu4 with y=0, 0.3, 0.7, and 1.0, are reported. The thermal conductivity is separated into the phonon thermal conductivity (κ ph ) (i.e., related to the heat carried by phonons) and into the electronic thermal conductivity (κ e ) (related to the heat carried by electrons). The electrical resistivity of the compounds was measured to determine the temperature dependence of the Lorenz number. The results show that in the temperature interval 4.2 to 300 K the latter quantity behavior follows the theoretical predictions for heavy fermion materials.
Published Version
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