The two physical parameters needed to specify the long-wavelength properties of a spin-1/2 quantum antiferromagnet are determined numerically. The fluctuation-induced renormalization of the stiffness constant differs by 40% from the expansion results of Oguchi, necessitating a corresponding adjustment in the value of the exchange deduced from the measured correlation length.

• Received 20 December 1988

DOI:https://doi.org/10.1103/PhysRevB.40.11328