  In this paper we present an extensive study of the thermodynamic properties
of the two-dimensional quantum Heisenberg antiferromagnet on the square
lattice; the problem is tackled by the pure-quantum self-consistent harmonic
approximation, previously applied to quantum spin systems with easy-plane
anisotropies, modeled to fit the peculiar features of an isotropic system.
Internal energy, specific heat, correlation functions, staggered
susceptibility, and correlation length are shown for different values of the
spin, and compared with the available high-temperature expansion and quantum
Monte Carlo results, as well as with the available experimental data.
