The Distinct Effects of Homogeneous Weak Disorder and Dilute Strong Scatterers on Phase Competetion in the Manganites

TL;DR

This study investigates how different types of disorder affect phase competition in manganites, revealing that homogeneous disorder suppresses charge and orbital order, while dilute strong scatterers induce phase separation.

Contribution

It provides the first spatially resolved analysis of the effects of weak homogeneous versus dilute strong disorder on phase competition in manganites.

Findings

Moderate homogeneous disorder suppresses CE-CO-OO phase and induces nanoscale glassy states.

Dilute strong scatterers lead to phase separation with ferromagnetic and AF-CO-OO clusters.

Results align with experimental observations in half-doped manganites.

Abstract

We study the two orbital double-exchange model in two dimensions in the presence of antiferromagnetic (AF) superexchange, strong Jahn-Teller coupling, and substitutional disorder. At hole doping x=0.5 we explore the `bicritical' regime where the energy of a ferromagnetic metal and a charge and orbital ordered (CO-OO) CE state are closely balanced, and compare the impact of weak homogeneous disorder to that of a low density of strong scatterers. Even moderate homogeneous disorder suppresses the CE-CO-OO phase and leads to a glass with nanoscale correlations. Dilute strong scatterers of comparable strength, however, convert the CE-CO-OO phase to a phase separated state with ferromagnetic and AF-CO-OO clusters. We provide the first spatial description of these phenomena and compare our results in detail to experiments on the half-doped manganites.