Recent experiments show that axially symmetric integer-spin antiferromagnetic chains undergo a phase transition at a critical applied magnetic field. It was argued, using Landau-Ginzburg theory, that this is one-dimensional Bose condensation. The theory is further analyzed at the mean-field and Gaussian level. Then some exact results concerning the critical behavior are determined using known results on one-dimensional Bose fluids. These are shown to be consistent with recent numerical simulations on spin chains. Breaking of axial symmetry produces crossover to a two-dimensional Ising transition.

• Received 10 July 1990

DOI:https://doi.org/10.1103/PhysRevB.43.3215