High-pressure synthesis and physical properties of perovskite and post-perovskite Ca1-xSrxIrO3

The post-perovskite (pPv) is the high-pressure phase of some highly distorted perovskites. The pPv phase of MgSiO3 stabilized under 125 GPa and 2000 K cannot be quenched to ambient pressure. In contrast, the pPv CaIrO3 can be synthesized under a modest pressure or even at ambient pressure. However, the pPv CaIrO3 has not been fully characterized. We report here systematic structural studies, measurements of transport and magnetic properties including critical phenomena, specific heat, and thermal conductivity in a series of samples Ca1-xSrxIrO3 synthesized under high pressure. The Ca1-xSrxIrO3 samples exhibit an evolution from the pPv phase to the perovskite phase. We have also prepared the perovskite (Pv phase) CaIrO3 with the wet chemical method. Rietveld refinements of the pPv and Pv phase CaIrO3 have been made based on high-resolution synchrotron diffraction. In comparison with effects of the chemical substitution on the crystal structure and physical properties, we have studied the structure and magnetic properties of the pPv CaIrO3 under hydrostatic pressure. Results have been discussed in the context of orbital ordering biased on the intrinsic structural distortion and the strong spin-orbit coupling that is much enhanced in these 5d oxides with the pPv structure.