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

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.

References in corpus (2)

• Hole-doping-induced changes in the electronic structure of La${}_{1-x}$Sr${}_x$FeO${}_3$ : soft x-ray photoemission and absorption study of epitaxial thin films
• Temperature-dependent soft x-ray photoemission and absorption studies of charge disproportionation in La${}_{1-x}$Sr${}_x$FeO${}_3$

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• Correlation of conductivity and angle integrated valence band photoemission characteristics in single crystal iron perovskites for 300 K < T < 800 K: Comparison of surface and bulk sensitive methods
• Correlation of high temperature X-ray photoemission spectral features and conductivity of epitaxially strained (La0.8Sr0.2)0.95Ni0.2Fe0.8O3/SrTiO3(110)