Structural and physical properties of 1:2 B-site-ordered perovskite Ba3CaIr2O9

Anomalous dielectric response in the triple perovskite ruthenate Ba3BiRu2O9

We have investigated the magnetic, dielectric and thermal properties of theSRu= 1 magnetic dimer Ba₃BiRu₂O₉, which is known to exhibit a spin-gap opening in conjunction with a first-order magneto-elastic phase transition at ∼175 K. Above the spin-gap temperature, the temperature dependence dielectric constant shows a peak like feature with pronounced frequency dependence. The critical slowing down behavior of this frequency dispersion suggests that a ferroelectric relaxor like electrical glassy state exists above the spin-gap opening temperature regime. The extermination of frequency dispersion-right at the magneto-elastic phase transition, is suggestive of a strong coupling between the lattice and charge-spin degrees of freedom in this triple perovskite system.

Frustration, strain and phase co-existence in the mixed valent hexagonal iridate Ba3NaIr2O9

Using detailed synchrotron diffraction, magnetization, thermodynamic and transport measurements, we investigate the relationship between the mixed valence of Ir, lattice strain and the resultant structural and magnetic ground states in the geometrically frustrated triple perovskite iridate Ba₃NaIr₂O₉. We observe a complex interplay between lattice strain and structural phase co-existence, which is typically not observed in this family of compounds. The low temperature magnetic ground state is characterized by the absence of long-range magnetic order, and points towards the condensation of a cluster glass state from an extended regime of short range magnetic correlations.