Critical dynamics of Heisenberg antiferromagnets: correlation functions above Neel point

Theory describing critical behavior of isotropic Heisenberg antiferromagnet s (AF) is proposed for a temperature range above the Neel point. It is show n that the critical dynamics of AF should be described in terms of relaxati on-diffusion mode coupling and the scaling behavior of spin diffusion coeff icient is determined by the scaling law for relaxation kinetic coefficient. The method based on analysis of diagrammatic expansion for diffusion and r elaxation constants allows incorporation of nonlocal spin-liquid correlatio ns. Applications of the method to heavy-fermion (HF) materials are briefly discussed. (C) 1999 Elsevier Science B.V. All rights reserved.