THE SPECIFIC-HEAT OF NDNI5

The specific heat of NdNi5 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-electrons subsystems. The conduction-electron subsystem is found in LaNi5 to be characterized by a value of the Sommerfeld coefficient gamma of 36 mJ/K2mol f.u. The contribution of the f-electron subsystem to the specific heat shows a lambda-type of peak at T(c) of 7.4 K and a non-pronounced Schottky-type of peak above T(c). The f contribution is well described within a single-ion Hamiltonian that includes the crystalline-electric-field (CEF) and exchange interactions of the Nd3+ ions. The exchange parameter and the full set of the CEF parameters associated with the hexagonal symmetry have been evaluated. The ground state GAMMA(s) for the Nd3+ ion in NdNi5 is highly anisotropic with the magnetic moment lying within the hexagonal plane. This ground-state results from higher-order charge multipolar interactions.