Study of Short-distance Spin and Charge Correlations and Local Density-of-States in the CMR regime of the One-Orbital Model for Manganites

Abstract

The metal-insulator transition, and the associated magnetic transition, in the colossal magnetoresistance (CMR) regime of the one-orbital model for manganites is here studied using Monte Carlo (MC) techniques. Both cooperative oxygen lattice distortions and a finite superexchange coupling among the $t_{2g}$ spins are included in our investigations. Charge and spin correlations are studied. In the CMR regime, a strong competition between the ferromagnetic metallic and antiferromagnetic charge-ordered insulating states is observed. This competition is shown to be important to understand the resistivity peak that appears near the critical temperature. Moreover, it is argued that the system is dynamically inhomogeneous, with short-range charge and spin correlations that slowly evolve with MC time, producing the glassy characteristics of the CMR state. The local density-of-states (LDOS) is also investigated, and a pseudogap (PG) is found to exist in the CMR temperature range. The width of the PG in the LDOS is calculated and directly compared with recent scanning-tunneling-spectroscopy (STS) experimental results. The agreement between our calculation and the experiment suggests that the depletion of the conductance at low bias observed experimentally is a reflection on the existence of a PG in the LDOS spectra, as opposed to a hard gap. The apparent homogeneity observed via STS techniques could be caused by the slow time characteristics of this probe. Faster experimental methods should unveil a rather inhomogeneous state in the CMR regime, as already observed in neutron scattering experiments.

arXiv comment13 pages, 10 figures

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• Recent Progress of Multiferroic Perovskite Manganites
• Quantum-Confinement-Induced Magnetism in LaNiO${}_3$-LaMnO${}_3$ Superlattices
• Theory of Strain-Controlled Magnetotransport and Stabilization of the Ferromagnetic Insulating Phase in Manganite Thin Films
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• Non-magnetic B-site Impurities Induce Ferromagnetic Tendencies in CE Manganites
• Charge and orbital order in transition metal oxides
• Fingerprint of dynamical charge/spin correlations in the tunneling spectra of colossal magnetoresistive manganites
• Evidence of mobile carriers with Charge Ordering gap in Epitaxial Pr${}_{0.625}$Ca${}_{0.375}$MnO${}_3$ Thin Films