Thermal conductivity of R2CuO4R2CuO4, with LaLa, Pr, and Gd

We present measurements of the in-plane (κabκab) and out-of-plane (κcκc) thermal conductivity of Pr2CuO4Pr2CuO4 and Gd2CuO4Gd2CuO4 single crystals. The anisotropy gives strong evidence for a large contribution of magnetic excitations to κabκab, i.e. for a heat current within the CuO2CuO2 planes. However, the absolute values of κmagκmag are lower than previous results on La2CuO4La2CuO4. These differences probably arise from deviations from the nominal oxygen stoichiometry. This has a drastic influence on κmagκmag, which is shown by an investigation of a La2CuO4+δLa2CuO4+δ polycrystal.