Paramagnetic susceptibilities of the antiferromagnetic quantum chain copper chloride bis-dimethyl sulfoxide: Theory and experiment.

Copper chloride bis(DMSO) (DMSO is dimethyl sulfoxide) consists of linear chains of antiferromagnetically coupled S=(1/2) ions. The single-crystal dc magnetic susceptibilities of both protonated and deuterated samples of this compound have been measured between 1.8 and 45 K; the susceptibilities of the two versions were identical. Evidence for a small amount of Ising-like anisotropy was seen in the temperature-dependent susceptibilities. The data were compared to the predictions of B\"ucher and Honerkamp for the behavior of single-crystal susceptibilities of XXZ linear chains. Good agreement was found for an exchange strength of J/${k}_{B}$=-8.25 K and an anisotropy parameter \ensuremath{\Delta}=1.1, slightly Ising-like. The b axis is the easy axis. The results of further theoretical studies on the effect of XXZ anisotropy upon powder susceptibilities of linear chains are presented. A procedure is described for determining both J and \ensuremath{\Delta} for XXZ antiferromagnetic chains from powder data.