MONTE-CARLO STUDY OF CRITICAL-BEHAVIOR IN THE 3-DIMENSIONAL CLASSICALHEISENBERG-FERROMAGNET

The static critical properties of classical, isotropic Heisenberg ferr omagnets have been studied numerically. Using an improved cluster algo rithm we performed extensive Monte Carlo simulations on L X L X L simp le cubic and body-centered cubic systems with L less-than-or-equal-to 40 over a temperature range covering the critical region. Temperature dependences of thermodynamic quantities were determined with an optimi zed multiple-histogram method, and both critical temperatures and crit ical exponents were extracted from finite-size scaling of several diff erent thermodynamic quantities. It was found that within their respect ive error bars the critical exponents for both ferromagnets agree with each other and with field theoretical predictions.