X-ray absorption fine structure (XANES and EXAFS)] study of The 6H-hexagonal mixed triple perovskites with formula Ba3AMM’O9 (A=Na, Mg, Pr,

The mixed triple perovskites Ba3AMM’O9 (A, mono, di-, tri-, and tetravalent cation; M, M’ being 4d & 5d transition metal, respectively) and face-sharing MM’O9 mixed dimers have now become a fertile ground for exotic quantum magnetism. The susceptibility shows single magnetic transition in Ba3NaRuIrO9 (combined Ru and Ir valence = 11), Ba3MgRuIrO9 (combined Ru and Ir valence = 10), and Ba3PrRuIrO9 (combined Ru and Ir valence = 9) near 100 K, 20 K and 3.5 K, respectively, while two magnetic anomalies for Ba3TbRuIrO9 (combined Ru and Ir valence = 9) at around 12 K & 5.5 K. The presence of local chemical disorder between A and Ir/Ru atoms and/or the atomic Ir- or Ru-clustering can change magnetic ground state. It is therefore an interesting to investigate the atomic site-order/disorder and accurately estimate the valence states of Pr/Tb, Ru & Ir in order to understand their magnetism. We propose to perform the Ru-K, Ir-L2, L3, Pr/Tb-L2, L3 edges XANES and EXAFS study on BM08.