iridates

Iridates are a class of compounds that contain iridium in oxide environments, typically oxides of iridium (IrO_x) or salts containing iridium–oxygen units. The term covers both discrete oxoanions of iridium and extended solid-state oxides. In most studies, the focus is on iridium in oxidation states +4 and higher; the IrO6 octahedra connect to form networks that range from one-dimensional chains to layered and three-dimensional perovskite-like frameworks.

Among the best-studied iridates are the layered Ruddlesden–Popper family A2IrO4 (A = Sr, Ba), where IrO6 octahedra form perovskite-like layers. The compound Sr2IrO4, in particular, has attracted attention as a spin-orbit Mott insulator with a J_eff = 1/2 state and canted antiferromagnetism. The three-dimensional perovskite SrIrO3 is metallic, illustrating the diversity of electronic behavior found in iridates. IrO2, a common rutile oxide, is frequently used as a catalyst and electrode material.

Electronic structure in iridates is strongly influenced by the large spin-orbit coupling of 5d electrons, which can split electronic manifolds and enhance correlation effects. This SOC-driven physics yields unconventional magnetic and electronic properties that are actively studied for potential applications in oxide electronics and quantum materials research.

Synthesis typically involves solid-state reactions at high temperatures between iridium oxides and other metal oxides, often under controlled oxygen partial pressure, and can proceed under hydrothermal or high-pressure conditions to form layered or post-perovskite phases. Iridates occur naturally as minerals and can be prepared for research purposes.

Name-wise, iridate refers to compounds containing iridium and oxygen; some contexts use iridate to denote oxoanions in solution, though solid-state oxides are the primary focus in materials science. Safety follows standard guidelines for heavy-metal compounds; iridium compounds are relatively low-toxicity but should be handled with care.