Inelastic Neutron Scattering study of magnetic excitations in triple perovskites Ba3RERuIrO9 (RE=Pr,Tb and Nd)

6H-perovskites with formula Ba3MAA´O9, which form in triple perovskite P63/mmc structure, display interesting magnetic properties on account of large spin-orbit coupling because of the shorter A-A´ distance in this structure. Among these the rare earth based triple perovskites Ba3PrRuIrO9, Ba3NdRuIrO9 and Ba3TbRuIrO9, which host 4f (RE), 4d (Ru) and 5d (Ir) moments and display fascinating magnetic properties with competing localized and itinerant magnetism, are of interest to us. Their magnetic susceptibility χ(T) data show magnetic phase transitions of antiferromagnetic nature near 3.4 K in Ba3PrRuIrO9, near 8 K in Ba3NdRuIrO9 and two phase transitions near 12.5 K and 5.5 K in Ba3TbRuIrO9. The χ(T) shows the complex nature of magnetic ordering in Ba3RERuIrO9 (RE = Pr, Nd and Tb) and reflects the presence of short-range ferromagnetic correlations along with the long-range antiferromagnetic correlations. Further investigations using the neutron scattering measurements are highly required to understand the magnetism and crystal field effect in Ba3RERuIrO9 (RE = Pr, Nd and Tb). We therefore propose to carry out inelastic neutron scattering experiment on Ba3RERuIrO9 (RE = Pr, Nd and Tb) using the MERLIN spectrometer to probe the magnetic excitations in these compounds.