Physical Properties of New Compounds RMg_2Ni_9 (R=La, Ce, Pr, Nd and Gd) with a Two Dimensional Rare Earth Arrangement

Abstract

We performed the magnetic susceptibility, specific heat and electrical resistivility measurements on RMg₂Ni₉ where R=La, Ce, Pr, Nd and Gd. RMg₂Ni₉ crystallizes in a hexagonal PuNi₃-type structure, in which the R atoms are in a two-dimensional arrangement. The results indicate that CeMg₂Ni₉ is a valence fluctuated compound with γ =80, mJ/mol· Ce· K², but the magnetic susceptibility and the electrical resistivility do not show any broad peak at a finite temperature. Even for R=Gd, no magnetic ordering is observed at 2, K. The unusual physical properties of RMg₂Ni₉ are obviously influenced by the two-dimensional arrangement of rare earth in the c-plane.