Spin Dependence of Correlations in Two-Dimensional Square-Lattice Quantum Heisenberg Antiferromagnets

We present a series expansion study of spin- $S$ square-lattice Heisenberg antiferromagnets. The numerical data are in excellent agreement with recent neutron scattering measurements. Our key result is that the correlation length $\xi$ for $S>\mathrm{}1\mathrm{}/2$ strongly deviates from the exact $T\to 0$ (renormalized classical) scaling prediction for all experimentally and numerically accessible temperatures. We note basic trends with $S$ of the experimental and series expansion correlation length data and propose a sequence of crossovers from renormalized classical to classical to Curie-Weiss regimes to explain them.