Optical absorption spectra and the nature of conduction carriers of hole-doped Sr1+xLa1-xFeO4

Takahisa Omata, Hiroyuki Ikawa, Satoru Fijitsu, Naoyuki Ueda, Hideo Hosono, Hiroshi Kawazoe

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The optical absorption as calculated from the diffuse reflectivity in the range of 0.5-5eV and the temperature dependence of d.c. electrical conductivity of Sr1+xLa1-xFeO4 (0 ≦ x ≦ 0.3) with a K2NiF4 structure, were measured. The results obtained were analyzed based on the small polaron model, and discussed with reference to the changes in the physical properties and the electronic structure previously reported. The Mott type and charge-transfer type excitations were observed at ∼2.2 and ∼2.7eV, respectively, in the optical absorption spectrum of the undoped SrLaFeO4. An additional broad absorption band below 1 eV was observed, and its intensity was directly proportional to the d.c. electrical conductivity at room temperature. Thus the absorption band below 1 eV was assigned to the optically induced polaron hopping. Based on the small polaron theory, the hopping energies of small polarons from 0.14 to 0.24 eV were obtained. These values were close to the activation energies of d.c. electrical conductivity obtained from the σT3/2 vs 1/T plots. The results, in which the Fermi-level was fixed in the middle of the energy band gap of the photoemission spectroscopy previously reported could not be explained by the rigid-band model, but were consistent with the small polaron model.

Original languageEnglish
Pages (from-to)411-415
Number of pages5
JournalSolid State Communications
Volume97
Issue number5
DOIs
Publication statusPublished - 1996 Feb
Externally publishedYes

Keywords

  • A. high-T superconductors
  • D. electron-electron interaction
  • D. electron-phonon interaction
  • D. electronic transport
  • D. optical properties

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry

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