The quasi-one-dimensional antiferromagnet CsMnCl3.2H2O. I. A random-phase approximation model

Abstract

A self-consistent random-phase approximation model has been used to simulate the magnetic properties of quasi-one-dimensional and three-dimensional antiferromagnets at low temperatures, and in various applied fields. To avoid problems associated with crystal-field terms, the authors have replaced the quadratic D(Sz2-1/2S(S+1)) term, which is responsible for easy-axis alignment, with anisotropic magnetic exchange. The resultant calculations have been used to discuss sublattice magnetisation, specific heats and nuclear-magnon coupling, in various applied fields, particularly near the antiferromagnetic-paramagnetic phase transition. Their principal conclusion is that magnetic moments in quasi-one-dimensional antiferromagnets are likely to be characterised by a large zero-point motion. This feature has important implications for nuclear orientation experiments in the milli-kelvin regime.