Correlation of high temperature X-ray photoemission spectral features   and conductivity of epitaxially strained   (La0.8Sr0.2)0.95Ni0.2Fe0.8O3/SrTiO3(110)
  Reversible and irreversible discontinuities at around 573 K and 823 K in the electric conductivity of a strained 175 nm thin film of (La0.8Sr0.2)0.95Ni0.2Fe0.8O3-{\delta} grown by pulsed laser deposition on SrTiO3 (110) are reflected by valence band changes as monitored in photoemission and oxygen K-edge x-ray absorption spectra. The irreversible jump at 823 K is attributed to depletion of doped electron holes and reduction of Fe4+ to Fe3+, as evidenced by oxygen and iron core level soft x-ray spectroscopy, and possibly of a chemical origin, whereas the reversible jump at 573 K possibly originates from structural changes. 
A. Braun, X. Zhang, Y. Sun, U. M\"uller, Z. Liu, S. Erat, M. Ari, H.   Grimmer, S. S. Mao, T. Graule
cond-mat.str-el