Sodium iridate (chemical formula NaIrO) is a sodium–iridium oxide that is geometrically frustrated, making it a strongly spin–orbit-coupled transition metal oxide. It is described as a hyperkagome iridate related to NaIrO, whose hyperkagome lattice is a three-dimensional network of corner-sharing triangular units. NaIrO is described as a 1/3-doped analogue of NaIrO (average Ir valence ≈ +4.33) and as semimetallic compared with the more insulating hyperkagome parent compound.
Structure Hyperkagome iridates are discussed as spinel-related (ordered-spinel) materials in which the Ir sublattice forms a three-dimensional network of corner-sharing triangles (the hyperkagome lattice). The hyperkagome can be viewed as a "deleted" pyrochlore-type network obtained by removing one-quarter of sites from a pyrochlore lattice. In iridates with Ir4+ (5d5), strong spin–orbit coupling entangles spin and t2g orbital character into effective Jeff = 1/2 moments, which is often used to motivate spin-liquid proposals for the hyperkagome lattice. NaIrO is described as a chiral, frustrated hyperkagome system and is commonly discussed as a doped member within the NaIrO family. Partial Na deintercalation from NaIrO can lead to a doped hyperkagome with NaIrO as an end member.
Physical properties
NaIrO demonstrates strong spin–orbit coupling combined with lattice-driven electronic-structure effects (including distortion-induced molecular orbitals in the hyperkagome setting). Because it combines a frustrated lattice with strong spin–orbit coupling and chiral structure, it has been suggested as a platform to explore unconventional electronic transport, including possible topological contributions.
See also
Kagome Lattice Quarter cubic honeycomb Quantum spin liquid
References