Tuning of Structure, Morphology and Magnetism in Postperovskite Oxide Solid Solutions

High-quality polycrystalline samples of type CaIr1-xPtxO3 solid solutions (x = 0.3, 0.5, 0.7) and CaIr0.5Rh0.5O3 have been synthesized at a pressure of 15 GPa, and their structures and properties are compared with those of CaIrO3. Substantial [100] grain growth is observed in all samples, leading to pronounced texture even in powdered materials. Small changes in the lattice constants and octahedral distortions are observed across the CaIr1-xPtxO3 series. CaIrO3 is semiconducting and shows temperature-independent paramagnetism and an ordered moment of 0.04 mu B below a 108 K magnetic transition. Doping with Pt or Rh induces Curie-Weiss paramagnetism and suppresses the magnetic transition to zero for similar to 40% Pt doping. The anisotropic structure and morphology of CaIrO3 combined with the Ir4+ spin-orbit coupling results in a large magnetic anisotropy constant of 1.77 x 10(6) J m(-3), comparable to values for permanent magnet materials.