FIRST-PRINCIPLES CALCULATION OF ANTIFERROMAGNETIC NMR ABSORPTION CURVES

We calculate nuclear-magnetic-resonance absorption curves for an assem bly of classical spins by combining numerical integration of the equat ions of motion with Monte Carlo simulations. Our technique is superior to traditional approaches especially when thermal fluctuations are la rge and the NMR peaks are broad. The results are used to explain and p redict NMR line shapes of copper nuclei below and above the antiferrom agnetic resonance is caused by thermal fluctuations which lift the gro und-state degeneracy.