Physical properties of the RNi4Cu (RÂ =Â rare earth) compounds

RNi4Cu (R = Y, Ce, Pr, Nd, Sm, Gd, Dy and Yb) compounds have been studied by means of the X-ray powder diffraction, magnetization, dc magnetic susceptibility, and electrical resistivity measurements. These compounds order ferromagnetically between 3.7 K (Pr) and 36.5 K (Gd). The temperature dependence of the electrical resistivity, ρ(T), reflects the metallic character of these compounds. Furthermore, the characteristic changes of the slope of the ρ(T) plots confirm the magnetic transitions. YNi4Cu is used as the nonmagnetic reference material. CeNi4Cu is paramagnetic and follows the modified Curie-Weiss law with μeff = 0.9 μB/f.u. This effective magnetic moment is much lower than the free Ce3+ ion value. At low temperatures ρ(T) reveals a shallow minimum characteristic of the Kondo-like effect. YbNi4Cu does not order magnetically down to 4 K. In the temperature range 100-300 K its magnetic susceptibility fulfills the Curie-Weiss law with the parameters θ = −195 K and μeff ≈ 5 μB/f.u. This effective magnetic moment is close to the value expected for the 4f13 configuration, i.e., 4.54 μB.