Estimation of single-ion anisotropies, crystal-field and exchange interactions in Gd-based frustrated pyrochlore anti-ferromagnets Gd2M2O7 (M=Ti, Sn, Hf, Zr)

The temperature dependence of the experimental results of dc (macroscopic) magnetic susceptibility and nuclear hyperfine properties of frustrated magnetic Gd-based pyrochlore compounds, Gd2Ti2O7, Gd2Sn2O7, Gd2Hf2O7 and Gd2Zr2O7, are analyzed within the frame work of appropriate crystal-field theory and a mean field approximation by introducing effective anisotropic molecular field tensors, and formulating an exact relation between single-ion susceptibility tensors and site susceptibility tensors. Components of the calculated susceptibility along and perpendicular to the local 〈1 1 1〉 axis of the tetrahedral sublattice of pyrochlore structure show that these pyrochlores are easy-planar anisotropic magnetic systems. The crystal-field parameters and anisotropic exchange coupling have been determined and their systematic variations over the Gd-based pyrochlores studied here are discussed.

► Site susceptibility tensors in pyrochlores Gd2M2O7 along and normal to local 〈1 1 1〉 axis of tetrahedra.
► Gd-pyrochlores are easy planar spin systems due to crystal-field and anisotropic exchange interaction.
► The crystal-field parameters and exchange interaction vary linearly with lattice constant.