CaMnIrO: An Anion-Deficient Perovskite Oxide Containing Ir.

Reaction between CaMnIrO and NaH, either through solid-solid contact or via a gas mediated reaction process, yields the topochemically reduced phase CaMnIrO in which Mn and Ir cations are located within a partially anion-vacancy disordered lattice. Magnetization data from CaMnIrO can be fit by the Curie-Weiss law to yield C = 1.586 cm K mol and θ = -86.

Structure and Magnetism of (La/Sr)MIrO and Topochemically Reduced (La/Sr)MIrO (M = Fe, Co) Complex Oxides.

Neutron powder diffraction data show that SrFeIrO, SrCoIrO, and LaSrCoIrO all adopt undistorted, n = 1 Ruddlesden-Popper structures in which the Ir and Fe/Co/Co cations are statistically disordered over all the octahedral coordination sites. Magnetization data indicate the two cobalt phases are spin glasses at low temperature, while SrFeIrO appears to adopt an antiferromagnetic state with very small magnetically ordered domains. Topochemical reduction with a Zr getter converts the tetragonal AMIrO phases to the corresponding orthorhombic AMIrO phases in which the Ir and Fe/Co/Co cations are located in approximately square-planar coordination sites.

SrFeIrO: Square-Planar Ir(II) in an Extended Oxide.

Topochemical reduction of the double-perovskite oxide SrFeIrO under dilute hydrogen leads to the formation of SrFeIrO. This phase consists of ordered infinite sheets of apex-linked FeO and IrO squares stacked with Sr cations and is the first report of Ir in an extended oxide phase. Plane-wave density functional theory calculations indicate high-spin Fe (d, S = 2) and low-spin Ir (d, S = /) configurations for the metals and confirm that both ions have a doubly occupied d orbital, a configuration that is emerging as a consistent feature of all layered oxide phases of this type.

Doped SrFeIrO-Phase Separation and a J ≠ 0 State for Ir.

High-resolution synchrotron X-ray and neutron powder diffraction data demonstrate that, in contrast to recent reports, SrFeIrO adopts an I1̅ symmetry double perovskite structure with an abc tilting distortion. This distorted structure does not tolerate cation substitution, with low levels of A-site (Ca, Ba, La) or Fe-site (Ga) substitution leading to separation into two phases: a stoichiometric I1̅ phase and a cation-substituted, P2/ n symmetry, aac distorted double perovskite phase. Magnetization, neutron diffraction, and Fe Mössbauer data show that, in common with SrFeIrO, the cation substituted SrA FeGa IrO phases undergo transitions to type-II antiferromagnetically ordered states at T ∼ 120 K.