Magnetic excitations of spin-orbital coupled Ir-Ir dimers in Ba3XIr2O9, X = Y or Sc

Studies of iridium-based compounds are at the forefront of solid state physics research. In these materials the electronic configurations are driven by strong spin-orbit coupling (SOC). We are currently investigating the spin frustration in an ambient pressure phase of Ba3YIr2O9 (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 on a hexagonal lattice. In Ba3YIr2O9 our zero-field muon spin rotation study reveals evidence of a long range magnetic ordering below 4 K, in agreement with heat capacity. Here we proposal to investigate the low energy magnetic excitations spectrum of Ba3YIr2O9 and Ba3ScIr2O9 using LET. Where in Ba3ScIr2O9 the effect of small scale Sc-Ir site disorder, TC = 9 K, will be investigated. This study will provide information on the intra-dimer and inter-dimer interactions as well as the effect of SOC on the spin gap, hence allowing modelling the spin-Hamiltonian of Ba3YIr2O9 and Ba3ScIr2O9. We have also submitted a neutron diffraction proposal on WISH to investigate the magnetic structure of Ba3YIr2O9, and Ba3ScIr2O9.