Influence of spin orbit coupling, crystal field effects, and exchange interactions on the ground state properties of double perovskites

In double perovskite compounds containing Ru4+ ions with 4d4 electronic configuration in a non-cubic local symmetry, the theoretical scenario of Jeff = 0 ground state breaks down due to competing spin-orbit coupling (SOC), crystal field effects, and super exchange interactions. We propose to perform XMCD experiments at the Ru L2 and L3 edges on La2ZnRuO6 and Sr2SnRuO6 double perovskites in monoclinic structure at three different temperatures. In these compounds, the B-site (B = Zn2+, Sn4+) ions consist of completely filled [Ar]d10 and [Kr]d10 electronic configurations. This situation possibly suppress the Ru-O-B-O-Ru super exchange paths. Consequently, the ground state is expected to be determined mainly by the SOC and crystal field effects. By applying the XMCD sum rules and the full multiplet cluster calculations within the configuration interaction approach, we can directly extract the ratio of orbital to spin moments. These investigations allow us to gain insights into (a) how reduction in the local symmetry changes the expected Jeff = 0 ground state and (b) how the super exchange interactions of Ru4+ d4 multiplet orbitals with completely filled d10 in comparison to empty d0 orbitals influence the ground state.