Symmetry Origin of the Phase Transitions and Phase Separation in Manganites at Low Doping

TL;DR

This paper investigates the symmetry-driven origins of phase transitions and phase separation in manganites, highlighting the role of magnetic order symmetry and proposing a Landau theory-based model for their competition.

Contribution

It reveals the symmetry basis of phase separation in manganites and introduces a simple theoretical model to explain the competition between magnetic phases.

Findings

Phase separation linked to noncollinear magnetic orders.

Symmetry changes govern phase transition pathways.

Landau theory effectively models phase competition.

Abstract

We analyze the symmetry changes of the paramagnetic to the A-type antiferromagnetic and to the ferromagnetic phase transitions in undoped and moderately doped LaMnO$_3$, respectively. We show that in the orthorhombic-distorted perovskite manganites the phase separation at low doping is associated with the noncollinear nature of the magnetic orders permitted by symmetry. A simple model for the competition between the two phase transitions is put forward within the framework of Landau theory of phase transitions.