Phase Separation Scenario for Manganese Oxides and Related Materials

TLDR

Computational studies of manganese oxides reveal a richer phase diagram than earlier 1950s–60s models, with phase segregation tendencies stronger than in cuprates. Including extended Coulomb interactions stabilizes a microscopically charged inhomogeneous state. The transition from antiferromagnetic insulator to ferromagnetic metal proceeds via mixed‑phase separation, which at low densities enhances charge fluctuations and is supported by experimental data.

Abstract

Recent computational studies of models for manganese oxides have revealed a rich phase diagram, which was not anticipated in early calculations in this context performed in the 1950s and 1960s. In particular, the transition between the antiferromagnetic insulator state of the hole-undoped limit and the ferromagnetic metal at finite hole density was found to occur through a mixed-phase process. When extended Coulomb interactions are included, a microscopically charged 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. Experimental data reviewed here by applying several techniques for manganites and other materials are consistent with this scenario. Similarities with results previously discussed in the context of cuprates are clear from this analysis, although the phase segregation tendencies in manganites appear stronger.