  Using the experimental data given in Phys. Rev. B70, 220507 (2004), we show
that -- unlike the effective coupling discussed in this paper -- the net
average antiferromagnetic interlayer coupling in doped lanthanum cuprates
depends only weakly on the doping or on the temperature. We argue that the
effective coupling is proportional to the square of the staggered
magnetization, and does not supply new information about the origin of the
suppression of the magnetic order in doped samples. Our analysis is based on a
modified version of the equation describing the spin-flip transition, which
takes into account the decrease of the staggered moment with temperature and
doping.
