Magnetic, electrical and thermodynamic properties of the UCu5Al7 derivatives

The discovery of heavy-fermion-like behavior in UCu4+xAl8-x ternaries has aroused the interest in the properties of their derivatives. Now, we report magnetic, electrical and thermodynamic properties of UCu4MAl7 alloys, where M=Cr, Mn, Ni. The substitution of the transition element for Cu changes only slightly the lattice parameters of the parent compound. The magnetic susceptibility of alloys with M=Cr and Ni is low and almost temperature independent. Mn alloy seems to exhibit magnetic ordering at low temperature because of the clear up-turn of the χ(T) plot. The field dependence of magnetization at 1.9 K exhibits a strong curvature at low magnetic field suggesting a ferromagnetic character. The extension of the measurements to magnetic field of 150 kOe and temperature to 4.2 and 77 K does not change the overall character of the M(B) plots. The magnetization versus magnetic field plots for the other two alloys are linear. The temperature dependence of inverse susceptibility follows modified Curie-Weiss law in a reasonably broad temperature range above about 50 K for the Cr and Ni alloys with the Weiss constants and effective magnetic moments very close to each other. In turn, χ-1(T) for the Mn compound shows two distinct parts. Electrical resistivity versus temperature plots are very similar in shape, and their numerical values are fairly close. The resistivity does not exhibit a metallic character, as far as temperature dependence is concerned. The thermodynamic data have been obtained from Figs through usual equations. The Debye temperatures are slightly higher than these obtained previously whereas the values of γ extrapolated from high and low temperature (not shown) are rather close to former data