Coexistence of Ferroelectricity and Ferromagnetism in a Rubidium Manganese Hexacyanoferrate

Multiferroic material: RbI0.82MnII0.20MnIII0.80[FeII(CN)6]0.80[FeIII(CN)6]0.14⋅H2O (see picture; MnII red octahedra, FeIII red spheres, MnIII blue octahedra, FeII blue spheres, CN white lines, gaps are Fe vacancies; H2O omitted) displays both ferroelectricity, explained by a mixing of FeII, FeIII, Fe vacancies, MnII, and Jahn–Teller-distorted MnIII centers, and ferromagnetism, caused by a parallel ordering of the magnetic spins of MnIII.