Low temperature heat capacities of one dimensional systems: Dimethylammonium trichlorocuprate (II) and tetramethylammonium trichloronickelate (II)

Abstract

The heat capacity of DMACuCl₃ has been measured from 1.156 to 28.608 K. The results indicate that three dimensional interactions are not negligible compared to those in one dimension. The one dimensional interactions may be interpreted in terms of the spin 1, antiferromagnetic Heisenberg model proposed by Weng and Griffiths, with an exchange parameter J of −4.92 K. Such a model is in agreement with a dimeric structure in which the Cu atoms are ferromagnetically coupled and in which the dimers within a chain order antiferromagnetically at low temperatures. The heat capacity of TMANiCl₃ has been measured from 0.639 to 27.432 K. The results indicate that three dimensional interactions are not negligible compared to those in one dimension. The results were fit to the spin 1, antiferromagnetic Heisenberg model proposed by Weng and Griffiths, with an exchange parameter J of −2.73 K. Although such a model yielded a good fit, the sign of the interaction is in disagreement with that found by initial susceptibility measurements.