Abstract
The Heisenberg pyrochlore antiferromagnet Gd2Pt2O7 is one of a series of gadolinium pyrochlore compounds with a variety of B-site cations. Despite the expected simplicity of a spin-only Gd3+ Heisenberg interaction model, the gadolinium pyrochlore series exhibits various complex magnetic ground states at low temperature. Gd2Pt2O7 displays the highest temperature magnetic order of the series with TN=1.6 K, which has been attributed to enhanced superexchange pathways facilitated by empty 5deg Pt orbitals. In this study, we use various neutron scattering techniques on an isotopically enriched polycrystalline 160Gd2Pt2O7 sample to examine the magnetic structure and spin-wave excitation spectrum below TN in order to extract the dominant exchange interactions. We find that the ground-state magnetic structure is the Palmer-Chalker state previously seen in Gd2Sn2O7 with an associated gapped excitation spectrum consistent with enhanced exchange interactions between further near-neighbor Gd3+ ions. We confirm this exchange model with analysis of the magnetic diffuse scattering in the paramagnetic regime using polarized neutrons.
