Disorder-induced orbital ordering in doped manganites

TL;DR

This study demonstrates that quenched disorder in doped manganites induces short-range orbital ordering, significantly increasing low-temperature resistivity and causing nanoscale inhomogeneity in magnetic properties.

Contribution

It reveals how disorder can induce orbital order and affect electronic and magnetic properties in a two-dimensional double-exchange model.

Findings

Disorder induces short-range orbital order near 30% doping.

Short-range orbital order correlates with increased low-temperature resistivity.

Magnetism becomes nanoscale inhomogeneous in the orbitally ordered state.

Abstract

We study the effect of quenched disorder on the ordering of orbital and magnetic degrees of freedom in a two-dimensional, two-band double-exchange model for $e_g$ electrons coupled to Jahn-Teller distortions. Using a real-space Monte Carlo method, we find that disorder can induce a short-range ordering of the orbital degrees of freedom near 30% hole doping. The most striking consequence of this short range ordering is a strong increase in the low temperature resistivity. The real-space approach allows to analyze the spatial patterns of the charge, orbital, and magnetic degrees of freedom, and the correlations among them. The magnetism is inhomogeneous on the nanoscale in the short-range orbitally ordered state.