Superconductivity of the Ni-based ternary compounds with AlB _2-type structure Y _2NiGe _3 and La _2NiGe _3

摘要

The crystal structure, electrical, and magnetic properties of the Ni-based ternary compounds Y _2NiGe _3 and La _2NiGe _3 have been investigated. Powder X-ray diffraction patterns reveal that both compounds crystallize in the AlB _2-derived hexagonal structure with values of the lattice parameters a = 4.066(7) and c = 4.025(1) for Y _2NiGe _3 and a = 4.180(2) and c = 4.334(1) for La _2NiGe _3. A sudden drop to zero value in the ρ(T) curves and the diamagnetic behavior observed in the χ _(ac)(T) curves conform the occurrence of bulk superconductivity in Y _2NiGe _3 and La _2NiGe _3 with T _C of 0.553 K and 0.394 K, respectively. Band structure calculations reveal that superconductivity in these two compounds is most probably from Y 4d electrons and La 5d electrons, respectively.