Nature of Partial Magnetic Order in the Frustrated Antiferromagnet Gd2Ti2O7
J A M Paddison, A B Cairns, D D Khalyavin, P Manuel, A Daoud-Aladine, G Ehlers, O A Petrenko, J S Gardner, H D Zhou, A L Goodwin, and J R Stewart
The frustrated pyrochlore antiferromagnet Gd2Ti2O7 has an unusual partially-ordered magnetic structure at the lowest measurable temperatures. This structure is currently believed to involve four magnetic propagation vectors k ∈ ⟨½ ½ ½⟩∗ in a cubic 4-k structure, based on analysis of magnetic diffuse-scattering data [J. Phys.: Condens. Matter 16, L321 (2004)]. Here, we present three pieces of evidence against the 4-k structure. First, we report single-crystal neutron-diffraction measurements as a function of applied magnetic field, which are consistent with the selective field-induced population of non-cubic magnetic domains. Second, we present evidence from high-resolution powder neutron-diffraction measurements that rhombohedral strains exist within magnetic domains, which may be generated by magneto-elastic coupling only for the alternative 1-k structure. Finally, we show that the argument previously used to rule out the 1-k structure is flawed, and demonstrate that magnetic diffuse-scattering data can actually be fitted quantitatively by a 1-k structure in which spin fluctuations on ordered and disordered magnetic sites are strongly coupled. Our results provide an experimental foundation on which to base theoretical descriptions of partially-ordered states.