Relevance of Cooperative Lattice Effects and Correlated Disorder in Phase-Separation Theories for CMR Manganites

TL;DR

This paper demonstrates that considering cooperative lattice effects and correlated disorder in phase-separation models aligns theoretical resistivity predictions with experimental observations in CMR manganites across different dimensions.

Contribution

It introduces the role of cooperative lattice distortions and correlated disorder in phase-separation theories, resolving dimensional discrepancies in resistivity calculations.

Findings

Resistor-network calculations show similar results in 2D and 3D when cooperative effects are included.

Correlated disorder leads to power-law correlations in quenched random fields.

The approach resolves the dimensionality discrepancy in phase-separated CMR models.

Abstract

Previous theoretical investigations of colossal magnetoresistance (CMR) materials explain this effect using a ``clustered'' state with preformed ferromagnetic islands that rapidly align their moments with increasing external magnetic fields. While qualitatively successful, explicit calculations indicate drastically different typical resistivity values in two- and three-dimensional lattices, contrary to experimental observations. This conceptual bottleneck in the phase-separated CMR scenario is resolved here considering the cooperative nature of the Mn-oxide lattice distortions. This induces power-law correlations in the quenched random fields used in toy models with phase competition. When these effects are incorporated, resistor-network calculations reveal very similar results in two and three dimensions, solving the puzzle.