We study theoretically the phase diagram of perovskite manganites taking into account the double degeneracy of the (Formula presented) orbitals in a (Formula presented) ion. A rich phase diagram is obtained in the mean-field theory at zero temperature as functions of (Formula presented) (hole concentration) and (Formula presented) (antiferromagnetic interaction between (Formula presented) spins). The global features of the phase diagram are understood in terms of the superexchange and double-exchange interactions, which strongly depend on the types of occupied (Formula presented) orbitals. The strong electron correlation induces the orbital polarization, which controls the dimension of the conduction band. A sequential change of the spin and orbital structures with doping holes is consistent with the recent experiments. In particular, a metallic (Formula presented)-type (layered) antiferromagnetic state is found for (Formula presented) with the uniform (Formula presented) orbital ordering. In this phase, calculated results suggest two-dimensional conduction and absence of the spin canting, which are observed experimentally. The effects of the Jahn-Teller distortion are also studied.
|Number of pages||14|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 1998 Jan 1|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics