Investigation of the Groundstates of 5d1 and 5d2 Osmate and Rhenate Double Perovskites by Neutron Powder Diffraction

Double perovskites hosting transition metals with 5d1 and 5d2 electronic configurations are widely considered as candidate materials hosting exotic physical groundstates from a theoretical standpoint. However, the characterization of these groundstates by neutron scattering has proven difficult. In this proposal, we aim to perform careful neutron powder diffraction measurements on a collection of 5d1 and 5d2 double perovskites, both rhenate and osmate variants (Ba2MgReO6, Ba2LaReO6, Ba2LiOsO6, and Ba2CaOsO6), possessing a range of observed physical properties in these systems. We plan to use the WISH diffractometer, which we consider to have the best possibility currently available in the global community to observe magnetic scattering from these small moments and determine the subtleties of the magnetic and crystal structures of these materials. The results are expected to have considerable impact on the understanding of spin-orbit coupled physics in heavy transition metal materials.