Colossal magnetoresistance observed in Monte Carlo simulations of the one- and two-orbital models for manganites

Cengiz Şen, Gonzalo Alvarez, Horacio Aliaga, Elbio Dagotto

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Abstract

The one- and two-orbital double-exchange models for manganites are studied using Monte Carlo computational techniques in the presence of a robust electron-phonon coupling (but neglecting the antiferromagnetic exchange JAF between the localized spins). The focus in this effort is on the analysis of charge transport. Our results for the one-orbital case confirm and extend previous recent investigations that showed the presence of robust peaks in the resistivity versus temperature curves for this model. Quenched disorder substantially enhances the magnitude of the effect, while magnetic fields drastically reduce the resistivity. A simple picture for the origin of these results is presented. It is also shown that even for the case of just one electron, the resistance curves present metallic and insulating regions by varying the temperature, as it occurs at finite electronic density. Moreover, in the present study these investigations are extended to the more realistic two-orbital model for manganites. The transport results for this model show large peaks in the resistivity versus temperature curves, located at approximately the Curie temperature, and with associated large magnetoresistance factors. Overall, the magnitude and shape of the effects discussed here resemble experiments for materials such as La0.70 Ca0.30 Mn O3, and they are in agreement with the current predominant theoretical view that competition between a metal and an insulator, enhanced by quenched disorder, is crucial to understanding the colossal magnetoresistance (CMR) phenomenon. However, it is argued that further work is still needed to fully grasp the experimentally observed CMR effect, since in several other Mn oxides an antiferromagnetic charge-ordered orbital-ordered state is the actual competitor of the ferromagnetic metal.

Original languageEnglish
Article number224441
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume73
Issue number22
DOIs
StatePublished - 2006

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