Thermodynamic properties of the haldane and non-haldane systems with the iso-structural compounds (CH3)4NM(NO2)3, M  Ni, Co

Abstract

In a one-dimensional compound (CH3)4NCo(NO2)3, which has the same crystal structure as (CH3)4NNi(NO2)3, we have found that next-nearest neighbor exchange interactions exist to frustrate the nearest neighbor interactions. A little larger Haldane gap energy obtained in the Ni2+ compound is suggested to be due to this kind of frustration.