  The field-theoretical result for the low-$T$ behaviour of the correlation
length of the quantum Heisenberg antiferromagnet on the square lattice was
recently improved by Hasenfratz [Eur. Phys. J. B {\bf 13}, 11 (2000)], who
corrected for cutoff effects. We show that starting from his expression, and
exploiting our knowledge of the classical thermodynamics of the model, it is
possible to take into account non-linear effects which are responsible for the
main features of the correlation length at intermediate temperature. Moreover,
we find that cutoff effects lead to the appearance of an effective exchange
integral depending on the very same renormalization coefficients derived in the
framework of the semiclassical {\em pure-quantum self-consistent harmonic
approximation}: The gap between quantum field-theoretical and semiclassical
results is here eventually bridged.
