Suppression of antiferromagnetic correlations by dipole-type impurities in lamellar cuprates

In doped lamellar cuprates, localized holes create ferromagnetic bonds and cause spin canting similar to that caused by magnetic dipoles. At low temperatures, these dipoles are frozen, behaving like quenched correlated random fields. Renormalization group methods are used to show that such impurities cause a strong reduction of the two-dimensional antiferromagnetic correlations in the non-linear $\sigma$ model, and a related decrease in the three dimensional N\'eel temperature, in quantitative agreement with experiments.