Magnetic Ordering of spin-orbital coupled Ir-Ir dimers in the Quantum Magnets: Ba3XIr2O9 X = Y, Sc

Studies of iridium-based compounds are at the forefront of condensed matter physics research in recent years. In these materials the electronic configurations are driven by strong spin-orbit coupling (SOC). We are currently investigating the spin frustration in of Ba3XIr2O9 X = Y or Sc (with Ir4.5+), using various experimental techniques, where one lone electron is shared over a structural Ir dimer, and a small magnetic moment order occurs for frustrated antiferromagnetic interactions in the presence of strong SOC. Our zero-field muon spin rotation study has revealed evidence of a small magnetic moment long range magnetic ordering below 4.5 K in Ba3YIr2O9, which disorder free. The site disorder between Ir and Sc sites increases the magnetic ordering temperature to 9 K in Ba3ScIr2O9, both in agreement with the heat capacity. The study of the magnetic ordering in these materials and related Ba3CdIr2O9 are highly limited by their unknown magnetic structure. Thus the proposed neutron diffraction study is to determine the magnetic structure of Ba3XIr2O (T=Y and Sc), which will help to understand the role of the lone electron shared across the Ir dimer, on a hexagonal lattice, in the presence of strong SOC.