SPECIFIC-HEAT OF ERNI5 AND DYNI5

The specific heat of DyNi5 measured on a single-crystalline specimen in the temperature interval from 1.5 K to 250 K has been analyzed in terms of two electronic subsystems. The conduction-electron subsystem is characterized by a value of the Sommerfeld coefficient gamma of 36 ml/K2 mol. The contribution of the rare-earth subsystem to the specific heat shows a lambda-type of peak at T(c) and above T(c) a Schottky-type of peak. The rare-earth contribution is well described within a single-ion Hamiltonian that includes the CEF and exchange interactions of the R3+ ions. The CEF interactions in ErNi5 and DyNi5 have been compared and a very similar charge multipolar distribution around the R3+ ions is found. The energy level scheme of these Kramers ions with J = 15/2 is derived.