x ray absorption fine structure (XAFS: combined XANES and EXAFS) Ba3MIr2O9 (M=Ti Zr)

The 6H-hexagonal perovskite iridates Ba3M4+Ir2O9 with Ir4+ ions located on the vertices of a triangular lattice have been serving as potential paradigm in search for novel quantum magnetic ground states. The M= Ti and Zr refute any kind of magnetic ordering in both the dc magnetization and specific heat data, despite having significant antiferromagnetic Ir-Ir exchange, promoting towards strongly quantum entangled spin liquid candidates. However, the presence of local chemical disorder as well as the mixed valency of Ir in the perovskite lattice disrupts the QSL phase, often giving rise to th spin-freezing phenomenon. At this point, it would be of extreme importance to have systematic investigation of the local atomic site-order/disorder and determination of the true Ir-valence, as well as to elucidate the effective spin-orbit coupling (SOC) strength in these two materials. So, we propose to perform the Ir-L2, L3 edges XAFS [combined XANES and EXAFS] study.