Orbital order in electron-doped manganites

Abstract

In electron-doped LaMnO3, La is partially substituted by tetravalent Ce, and Mn has a valence between 2 and 3. Mn2+ ions have five localized 3d electrons (half-filled shell) and a spin S*=5∕2. The Mn3+ configuration corresponds to an eg hole in the half-filled shell yielding a total spin S=2. A mean-field slave-boson formulation for hole doping has been extended to electron doping. For eg holes in two orbitals with excluded multiple occupancy and Hund’s rule coupling between the eg and t2g states, we study the conditions for staggered orbital order in the A phase for electron doping. The long-range staggered order of the eg orbitals arises due to the competition of the superexchange, the double exchange, and the Jahn–Teller effect.