Electrical and magnetic properties of the Ni based ternary ompounds R 2NiGe3 (R Rare Earth Ions)

Abstract

The crystal structure, electrical, and magnetic properties of the Ni based ternary compounds R2NiGe3 (R rare earth ions) have been investigated using powder X-ray diffraction, electrical resistivity, and magnetic susceptibility measurements. X-ray diffraction patterns reveal that all the samples studied crystallize in the AlB2-derived hexagonal structure with space P6/mmm and the obtained values of the lattice constants a and c are a 0.4188(1) nm and c 0.4339(3) nm for La2NiGe3 and the lattice constants are found to decrease monotonically with increasing atomic number of R. A sudden drop to zero value in the ρ(T) curve reveals that La2NiGe3 becomes superconducting with a midpoint transition temperature TC of ∼ 0.45 K. The χ(T) curves for all samples studied follow the Curie-Weiss behavior for T > 100 K, with the obtained value of effective moment μ4eff close to the moment of the corresponding R3+ ions. The occurrence of peak in the χ(T) curve and a drop off in the ρ(T) curve at the corresponding temperatures indicate that antiferromagnetic transition occurs below 10 K in Gd 2NiGe3 and Dy2NiGe3. In addition, Pr2NiGe3 and Ho2NiGe3 also become magnetically ordered at low temperatures as inferred from the drop off in the ρ(T) curve and the anomaly in the χ(T) curves in these compounds. The existence of minimun at 18 K followed by a -lnT dependence below 18 K in the ρ(T) curve and a T1/2 dependence in the χ(T) curve observed for Ce2NiGe3 reveal characteristic of a Kondo lattice in this compound. © Published under licence by IOP Publishing Ltd.