The correlation length of the Heisenberg antiferromagnet with arbitrary spin S

Experiments and numerical data on the correlation length for large S disagree strongly with the theoretical prediction based on the effective field theory prescription of the magnon physics. The reason is that for large S, at any accessible , the cut-off effects from the non-magnon scales become large and can not be treated by an effective field theory. We study these effects in a spin-wave expansion. The corrected prediction on connects the renormalized classical and the classical scaling regions smoothly and comes close to the data.