Unveiling First Order CMR Transitions in the Two-Orbital Model for Manganites

TL;DR

This study uses large-scale Monte Carlo simulations to reveal that colossal magnetoresistance in a two-orbital manganite model occurs via a first-order transition, aligning theory with experimental observations and persisting under disorder.

Contribution

It demonstrates that CMR transitions in the two-orbital manganite model are first order in certain regions, resolving previous discrepancies between theory and experiments.

Findings

CMR ratio ~10,000% observed.

First-order transition confirmed in the phase diagram.

Transition characteristics are robust under weak disorder.

Abstract

Large scale Monte Carlo simulation results for the two-orbital model for manganites, including Jahn-Teller lattice distortions, are here presented. At hole density x=1/4 and in the vicinity of the region of competition between the ferromagnetic metallic and spin-charge-orbital ordered insulating phases, the colossal magnetoresistance (CMR) phenomenon is observed with a magnetoresistance ratio ~10,000% Our main result is that this CMR transition is found to be of first order in some portions of the phase diagram, in agreement with early results from neutron scattering, specific heat, and magnetization, thus solving a notorious discrepancy between experiments and previous theoretical studies. The first-order characteristics of the transition survive, and are actually enhanced, when weak quenched disorder is introduced.