Phase Diagram and Incommensurate Phases in Undoped Manganites

TL;DR

This paper investigates the phase diagram of undoped manganites, revealing temperature-induced commensurate-incommensurate transitions driven by competing magnetic interactions.

Contribution

It provides a theoretical analysis of incommensurate phases in undoped manganites, aligning with experimental observations and elucidating the role of competing interactions.

Findings

Temperature-induced phase transitions observed in models.

Incommensurate magnetic wave vector varies with temperature.

Competition between superexchange and double exchange causes incommensurate phases.

Abstract

We study the existence of incommensurate phases in the phase diagram of the two orbital double exchange model coupled with Jahn-Teller phonons and with superexchange interactions. In agreement with experimental results, we find that undoped manganites $RMnO_3$ ($R$ being some rare earth element) show temperature induced commensurate-incommensurate phase transitions. In the incommensurate phase the magnetic wave vector varies with temperature. The incommensurate phase arises from the competition between the short range antiferromagnetic superexchange interaction and the long range ferromagnetic double exchange interaction.