Competing Effects in Perovskite Manganites: Ferromagnetism vs. Phase Separation

Abstract

This paper is an informal and brief review of the present status of the computational studies of models for manganites that recently reported the existence of phase separation at low temperatures (S. Yunoki et al., Phys. Rev. Lett. 80, 845 (1998); 81, 5612 (1998); A. Moreo et al., cond-mat/9901057 (to appear in Science)). Results for both the one-orbital and two-orbital models, the latter with Jahn-Teller phonons, are included. The main finding is that the transition between the insulating state of the hole-undoped limit and the ferromagnetic metallic state at finite hole-density occurs through a mixed-phase process. When long-range Coulomb interactions are included, a microscopically charge inhomogeneous state should be stabilized. These phase separation tendencies, also present at low electronic densities, influence the properties of the ferromagnetic region by increasing charge fluctuations. A large Hst of experimental results are compatible with the existence of charge-inhomogeneities in the manganites, which may be an important ingredient for the explanation of the CMR effect in these compounds.KeywordsMonte CarloDouble ExchangePerovskite ManganiteKondo ModelRich Phase DiagramThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.