Suppression of critical properties in doped cuprates

In high-Tc superconductors dopant atoms supply holes or excess electrons. Electric conduction happens in the neighbourhood of dopants within a circle several lattice constants wide. Percolation of these conducting areas leads to global conduction. Diffusing d-electrons in these areas can destroy antiferromagnetism: the Neel temperatures decrease with doping. Based on an Ising model with antiferromagnetic interactions acting in the part of the lattice not covered by conducting areas, the specific heat, the staggered susceptibility and the spin correlation lengths show very broad peaks even for low dopant concentrations. In doped cuprates, due to the small size granularity comparable with the sizes of our simulated systems, possible peak height singularities are always suppressed.