STATIC CRITICAL-BEHAVIOR OF 3-DIMENSIONAL CLASSICAL HEISENBERG MODELS- A HIGH-RESOLUTION MONTE-CARLO STUDY

Using both recently developed cluster-algorithm and histogram methods, we have carried out a high-resolution Monte Carlo study of static cri tical properties of classical ferromagnetic Heisenberg models. Extensi ve Monte Carlo simulations were performed at several temperatures in t he critical region, using an improved cluster-updating scheme, on L X L X L simple-cubic and body-centered-cubic systems with L less-than-or -equal-to 40. Thermodynamic quantities as a function of temperature in the vicinity of the critical point were obtained by an optimized mult iple-histogram method, and the critical temperature and static critica l exponents were extracted using finite-size scaling. Our best estimat es for the inverse critical temperatures are 0.693 035(37) for the sim ple-cubic system and 0.486 798(12) for the body-centered-cubic system. Estimated static critical exponents for both systems agree with each other within their respective error bars, and the mean estimates nu = 0.7048(30) and gamma = 1.3873(85) are also in excellent agreement with field-theoretic predictions 0.705(3) and 1.386(4).