Competing Ferromagnetic and Charge-Ordered States in Models for Manganites: the Origin of the CMR Effect

TL;DR

This paper uses large-scale Monte Carlo simulations to explore the competition between ferromagnetic and charge-ordered states in manganite models, revealing the origin of colossal magnetoresistance effects near a bicritical point.

Contribution

It provides new insights into the microscopic mechanisms behind CMR by analyzing the interplay of magnetic and charge orderings in manganite models.

Findings

Identification of a regime with competing FM and CO states at specific doping levels.

Observation of CMR effects near the bicritical point due to short-range polaron correlations.

Development of charge correlations resembling low-temperature CO states above spin ordering temperatures.

Abstract

The one-orbital model for manganites with cooperative phonons and superexchange coupling $J_{\rm AF}$ has been investigated via large-scale Monte Carlo (MC) simulations. Results for two-orbitals are also briefly discussed. Focusing on electronic density $n$=0.75, a regime of competition between ferromagnetic (FM) metallic and charge-ordered (CO) insulating states was identified. In the vicinity of the associated bicritical point, colossal magnetoresistance (CMR) effects were observed. The CMR is associated with the development of short-distance correlations among polarons, above the spin ordering temperatures, resembling the charge arrangement of the low-temperature CO state.