Average Lattice Symmetry and Nanoscale Structural Correlations in Magnetoresistive Manganites

Abstract

We report x-ray scattering studies of nanoscale structural correlations in the paramagnetic phases of the perovskite manganites La${}_{0.75}$(Ca${}_{0.45}$Sr${}_{0.55}$)${}_{0.25}$MnO${}_3$, La${}_{0.625}$Sr${}_{0.375}$MnO${}_3$, and Nd${}_{0.45}$Sr${}_{0.55}$MnO${}_3$. We find that these correlations are present in the orthorhombic $O$ phase in La${}_{0.75}$(Ca${}_{0.45}$Sr${}_{0.55}$)${}_{0.25}$MnO${}_3$, but they disappear abruptly at the orthorhombic-to-rhombohedral transition in this compound. The orthorhombic phase exhibits increased electrical resistivity and reduced ferromagnetic coupling, in agreement with the association of the nanoscale correlations with insulating regions. In contrast, the correlations were not detected in the two other compounds, which exhibit rhombohedral and tetragonal phases. Based on these results, as well as on previously published work, we propose that the local structure of the paramagnetic phase correlates strongly with the average lattice symmetry, and that the nanoscale correlations are an important factor distinguishing the insulating and the metallic phases in these compounds.

a note on recent experimental work, and a new reference added

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Cited by in corpus (7)

• Polaronic excitations in CMR manganite films
• A-site Ordering versus Electronic Inhomogeneity in CMR-Manganite Films
• Percolative phase transition on ferromagnetic insulator manganites: uncorrelated to correlated polaron clusters
• Uncorrelated and correlated nanoscale lattice distortions in the paramagnetic phase of magnetoresistive manganites
• Electron coherent and incoherent pairing instabilities in inhomogeneous bipartite and nonbipartite nanoclusters
• Substrate-induced strain effects on Pr_{0.6}Ca_{0.4}MnO_{3} films
• Non percolative nature of the metal-insulator transition and persistence of local Jahn-Teller distortions in the rhombohedral regime of La${}_{1-x}$Ca${}_x$MnO${}_3$