We discovered a new iridate, Sr9Ir3O17, which is the first reported transition metal oxide containing a low-spin, tetrahedrally coordinated ion in the solid state.
Significance and Impact
Sr9Ir3O17 challenges crystal chemical norms that tetrahedra with partially occupied d-states are high-spin and provides a recipe for designing other such violators.
- Sr9Ir3O17 contains IrO6 octahedra and IrO4 tetrahedra; electronic structure corroborated by X-ray absorption near edge spectroscopy, magnetic susceptibility and DFT with inclusion of spin-orbit coupling and electron correlation.
- Local spin models do not explain magnetic susceptibility, reflecting strong Ir-O hybridization and requiring description in terms of the IrO4 and IrO6 clusters.
- Ir5+ (d4) in the tetrahedron maximizes the crystal field stabilization energy of the low spin e4t20 configuration by exploiting the strong overlap between Ir 5d and O 2p orbitals.
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