Charge stacking in the half-doped manganites

The stability of the charge-stacked structure vis-a-vis the charge-alternate structure in the half-doped manganites is studied with a model that includes electronic kinetic energy, onsite and intersite Coulomb interactions, the Jahn-Teller energy, and the antiferromagnetic superexchange between the manganese core spins. It is shown that for a single zigzag chain, the electronic kinetic energy stabilizes the standard chain, with Mn3+ at the bridge site and Mn4+ at the corner site, over the reversed zigzag chain with the two Mn valences interchanged. The electronic kinetic energy and magnetic interactions stabilize the three-dimensional charge-stacked structure, while a large intersite Coulomb interaction Vgreater than or equal toV(c) would stabilize the charge-alternate structure. It is argued that the magnitude of V is small enough that the charge-stacked structure is stabilized in the half-doped manganites such as La1/2Ca1/2MnO3. (C) 2002 American Institute of Physics.