RMnO3type

RMnO3-type refers to a family of oxides with the general formula RMnO3, where R is a rare-earth element (or a similar large cation) and Mn sits in octahedral coordination with oxygen. These compounds are most commonly discussed as part of the perovskite oxide class, where Mn3+ ions provide a rich set of electronic and magnetic interactions. The RMnO3 family also includes structural variants such as hexagonal polymorphs that occur for smaller R ions, illustrating the close link between ionic size, structure, and properties.

In the archetypal perovskite RMnO3, the crystal framework is built from corner-sharing MnO6 octahedra with the larger R cation occupying the A-site cavities. The Mn3+ ions exhibit Jahn-Teller activity, which drives distortions of the MnO6 octahedra and tilting of the octahedra (often described as GdFeO3-type tilts). These distortions lift electronic degeneracies and strongly influence magnetic exchange pathways. The resulting structure is typically orthorhombic (space group Pbnm) for many RMnO3 compounds, though the hexagonal phase is favored for sufficiently small R ions.

Physically, RMnO3-type materials are insulating and display complex magnetic order at low temperatures, arising from Mn3+ spins. The exact magnetic ground state—often antiferromagnetic with subtle canting—depends on the R ion and structural details. Some members also exhibit coupled or competing spin and lattice phenomena, and certain RMnO3 compounds (notably some Tb- and Dy-based systems) are of interest for magnetoelectric or multiferroic behavior, where magnetic order is linked to electric polarization.

Synthesis typically involves solid-state methods with precise control of stoichiometry and oxygen content. RMnO3-type materials serve as model systems for studying orbital ordering, Jahn-Teller distortions, and magnetoelectric coupling in transition-metal oxides.