Inhomogeneous Ferromagnetism and Unconventional Charge Dynamics in Disordered Double Exchange Magnets

TL;DR

This paper investigates the effects of disorder on double exchange ferromagnets, revealing inhomogeneous magnetic states and unconventional charge dynamics through large-scale, self-consistent simulations.

Contribution

It introduces a self-consistent method to analyze disordered double exchange models, providing exact results on magnetic and charge properties in large systems.

Findings

Inhomogeneous ferromagnetic states are stabilized by disorder.

Charge dynamics show unconventional behavior compared to clean systems.

Results align with experimental observations in disordered manganites.

Abstract

We solve the double exchange model in the presence of arbitrary substitutional disorder by using a self consistently generated effective Hamiltonian for the spin degrees of freedom. The magnetic properties are studied through classical Monte Carlo while the effective exchange, $D_{ij}$, are calculated by solving the disordered fermion problem, and renormalised self-consistently with increasing temperature. We present exact results on the conductivity, magnetoresistance, optical response and `real space' structure of the inhomogeneous ferromagnetic state, and compare our results with charge dynamics in disordered La_{1-x}Sr_xMnO_3. The large sizes, ${\cal O} (10^3)$, accessible within our method allows a complete, controlled calculation on the disordered strongly interacting problem.