Magnetic Phase Transition of Ni(NH3)2Ni(CN)4·2C12H10

Abstract

The magnetic susceptibility and the specific heat of Ni(NH 3 ) 2 Ni(CN 4 )·2C 12 H 10 have been measured between 0.35 K and 20 K on a powder specimen. The crystalline-field splitting energy of the Ni ++ -ion spin triplet is estimated to be 2.5±0.3 K with doublet ground state ( S z =±1). Together with a layer structure of the magnetic ions in this clathrate compound, the magnetic spins can be regarded as forming a two-dimensional Ising-like system. A symmetric logarithmic divergence of the specific heat is actually observed at T N =0.800±0.005 K.