Comment on “Strong dependence of the interlayer coupling on the hole mobility in antiferromagnetic ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x\mathrm{Cu}{\mathrm{O}}_4$ $(x<0.02)$”

Using the experimental data given in the above paper, 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.

Figure 1

The ratio $\alpha =H_c∕M_F$ versus temperature for lanthanum cuprate doped with Sr (concentration $x$), Zn $\left(z\right)$, and Eu $\left(y\right)$. The experimental data are taken from Refs. 2, 3. The typical error bars are from Table I in Ref. 2. “s” and “p” stand for single and polycrystal samples.