A low spin tetrahedron in a 5 d transition metal oxide

July 30, 2019

In a study published in Physical Review Materials, researchers discovered that low spin state for a tetrahedral environment provides a novel platform for spin state manipulation in solid state materials.

(a) Crystal structure of Sr9Ir3O17. IrO6 octahedra and IrO4 tetrahedra are shown in blue, Sr atoms are shown in purple. (b) Representative IrO6 octahedron with the blue ellipsoid representing Ir and red ellipsoids representing O. (c) IrO4 tetrahedron with the black ellipsoid representing Ir and red ellipsoids representing O. In (b) and (c) symmetry unique Ir-O distances are shown.

Scientific Achievement

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.

Research Details

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 5 d and O 2p orbitals.

DOI: 10.1103/PhysRevMaterials.3.063607

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