Landau model for the phase diagrams of the orthorhombic rare-earth manganites RMnO3

TL;DR

This paper develops a Landau theory-based model to describe the complex phase transition sequences in orthorhombic rare-earth manganites RMnO3, unifying their phase diagrams and modulated phases.

Contribution

It introduces a single phenomenological Landau model that captures the phase transitions and modulated phases of RMnO3 compounds at zero magnetic field.

Findings

Successfully describes the phase transition sequence in RMnO3

Unifies temperature and composition phase diagrams

Provides a theoretical framework for modulated phases

Abstract

The present work aims to describe, within a single phenomenological approach, the specific sequence of phase transitions observed in the rare-earth manganites RMnO3 at zero magnetic field. It is shown that a single integrated description of the temperature versus composition phase diagrams of these compounds and related solid solutions can be obtained within the scope of Landau theory by adopting the so called type-II description of the modulated phases.