Phase Transition in NixCd(1-x)(NH3)2·Ni(CN)4·2C6H6

Abstract

The magnetic phase transition in the antiferromagnetic Ising spin system diluted with non-magnetic atoms, Ni _x Cd _{(1- x )} (NH ₃ ) ₂ ·Ni(CN) ₄ ·2C ₆ H ₆ , was studied by the specific heat measurement. The dependence of the Néel point T _N ( x ) on concentration x for Ni ²⁺ ions was obtained. The critical concentration x _c , below which magnetic order did not exist, was 0.65. Broad maximum of the Schottky-type due to short range order was observed and the curve of specific heat at x _c =0.65 was well fitted to the exact solution of the Ising linear chain model suggesting that the effective dimensionality of spin system was decreased by random dilution. The singular point of specific heat was reduced to a cusp by the effect of dilution.