Spin polaron electronic structure of La0.5Ca0.5MnO3: UHF and CI calculations

Abstract Unrestricted Hartree–Fock and cluster configuration interaction calculations on La0.5Ca0.5MnO3 show that the electronic structures of these compounds consist of small spin polarons in which a fraction of oxygen ions are essentially O− rather than O2− and Mn ions are all essentially Mn2+. Exchange coupling within the polarons is strong (>200 meV ) , whereas exchange coupling between polarons is much weaker (∼10 meV ) .