Exchange interactions in antiferromagnetic salts of iridium III. Theory of the interaction

Abstract

A theoretical description is given of the interaction between two iridium ions, each surrounded by an octahedron of chlorine ions, in a semi-dilute crystal. Group theory is used to classify the states and to examine the various contributions to the Hamiltonian. The lowest energy level of the two iridium-chlorine complexes is a quadruplet, which breaks up under the inter­action into a singlet and a triplet. The singlet-triplet separation and also the splitting of the triplet are related to various exchange integrals, and it is shown that the arrangement of the energy levels is a consequence of the directional nature of p -orbitals on the chlorine sites.