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Percolative phase transition on ferromagnetic insulator manganites: uncorrelated to correlated polaron clusters

A. M. L. Lopes·J. P. Araujo·J. J. Ramasco·E. Rita·V. S. Amaral·J. G. Correia·R. Suryanarayanan·the ISOLDE Collaboration
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Abstract

In this work, we report an atomic scale study on the ferromagnetic insulator manganite LaMnO$_{3.12}$ using $γ-γ$ PAC spectroscopy. Data analysis reveals a nanoscopic transition from an undistorted to a Jahn-Teller-distorted local environment upon cooling. The percolation thresholds of the two local environments enclose a macroscopic structural transition (Rhombohedric-Orthorhombic). Two distinct regimes of JT-distortions were found: a high temperature regime where uncorrelated polaron clusters with severe distortions of the Mn$^{3+}$O$_{6}$ octahedra survive up to $T \approx 800 K$ and a low temperature regime where correlated regions have a weaker JT-distorted symmetry.

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A. M. L. Lopes, J. P. Araujo, J. J. Ramasco, E. Rita, V. S. Amaral, J. G. Correia, R. Suryanarayanan, the ISOLDE Collaboration. 2005-11-03. Percolative phase transition on ferromagnetic insulator manganites: uncorrelated to correlated polaron clusters. https://doi.org/10.1103/physrevb.73.100408

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