Universal magnetic properties of La2-SrCuO4 at intermediate temperatures

We present the theory of two-dimensional, clean quantum antiferromagnets with a small, positive, zero temperature (T) stiffness 5, but with the ratio kBT/s arbitrary. Universal scaling forms for the uniform susceptibility (u), correlation length, and NMR relaxation rate (1/T1) are proposed and computed in a 1/N expansion and by Monte Carlo simulations. For large kBT/s, u(T)/T and T(T) asymptote to universal values, while 1/T1(T) is nearly T independent. We find good quantitative agreement with experiments and some numerical studies on La2-SrCuO4.