The specific heat of NdNi/sub 5/

The specific heat of NdNi/sub 5/ measured on a single-crystalline specimen from 1.5 K to 250 K has been analyzed in terms of two electronic subsystems, i.e. conduction-electron and f-electron subsystems. The conduction-electron subsystem is found in LaNi/sub 5/ to be characterized by a value of the Sommerfeld coefficient /spl gamma/ of 36 mJ/K/sup 2/mol f.u. The contribution of the f-electron subsystem to the specific heat shows a /spl lambda/-type of peak at T/sub c/ of 7.4 K and a non-pronounced Schottky-type of peak above T/sub c/. The f contribution is well described within a single-ion Hamiltonian that includes the crystalline-electric-field (CEF) and exchange interactions of the Nd/sup 3+/ ions. The exchange parameter and the full set of the CEF parameters associated with the hexagonal symmetry have been evaluated. The ground state /spl Gammasub 8/ for the Nd/sup 3+/ ion in NdNi/sub 5/ is highly anisotropic with the magnetic moment lying within the hexagonal plane. This ground-state results from higher-order charge multipolar interactions.<
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