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arXiv · 1106.1014

Electron hole - phonon interaction and structural changes in La0.9Sr0.1FeO3 by temperature dependent conductivity and valence band photoemission spectros-copy

A. Braun·J. Richter·A. S. Harvey·A. Infortuna·A. Frei·E. Pomjakushina·Bongjin S. Mun·P. Holtappels·U. Vogt·K. Conder·L. J. Gauckler·T. Graule
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Abstract

Electric conductivity and structural details of the hole-doped polaron conductor La0.9Sr0.1FeO3 (LSF10) are reported. The conductivity of a single crystal shows an exponential increase with temperature with a maxi-mum of 100 S/cm at 700 K and with activation energy of about 375 meV, and a decrease for higher temperatures that follows a power law. The exponential increase of the electric conductivity for 300 K {\leg} T {\leg} 700 is accompanied by a shift of spectral weight in the photoemission valence band towards the Fermi level, indicative of a strong electron-phonon interaction. The subsequent decrease of the conductivity for T > 700 K is accompanied by a reversible phase transformation from orthorhombic to rhombohedral symmetry. The decreasing conductivity for T > 700 K is likely due to the reduction of the iron due to oxygen loss causing a decreasing hole concentration, as evidenced by a substantial chemical shift in the Fe K-shell x-ray absorption spectra. Two additional fine structures in the conductivity data at 357 K, this is, a small temperature reversible jump in the conductivity, and at 573 K, a slight reversible increase of the polaron activation energy, are correlated with an exceptionally strong decrease in spectral valence band intensity near the Fermi level, and with the onset of a corresponding structural transition.

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A. Braun, J. Richter, A. S. Harvey, A. Infortuna, A. Frei, E. Pomjakushina, Bongjin S. Mun, P. Holtappels, U. Vogt, K. Conder, L. J. Gauckler, T. Graule. 2011-06-06. Electron hole - phonon interaction and structural changes in La0.9Sr0.1FeO3 by temperature dependent conductivity and valence band photoemission spectros-copy. https://doi.org/10.1063/1.3049614

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