Effect of Annealing on Valence Electronic States Related to Mn Ions of La0.67Sr0.33MnO3 Films

La0.67Sr0.33MnO3 (LSMO) films were prepared on SrTiO3 single-crystal substrates by the pulsed laser deposition method. X-ray photoelectron spectra (XPS) were measured for the LSMO films as-prepared and annealed in vacuum, respectively. Multiple peak fitting for Mn 2p3/2 XPS spectra shows that Mn3+ and Mn4+ proportionally decrease on the surface of the LSMO film annealed in vacuum compared with the as-prepared film. And the saturation magnetization (Ms) slightly decreases. Analysis indicates that a small amount of Mn2+, as surface defects of LSMO films, hardly changed after vacuum annealing. The total of Mn3+, Mn4+ and the low-binding energy peak (LEP) remains unchanged before and after annealing in vacuum, which suggests that LEP should be related with Mn3+ and Mn4+ when the magnetic properties are considered.

X-ray Photoelectron Studies of High-temperature Superconductors: Evidence for the Importance of Alkaline Earth Metals

All high�temperature superconducting ceramics so far studied contain alkaline-earth ions, and in all cases core-level X-ray photoelectron spectroscopy shows an anomalous low-binding energy peak from these ions. We argue that this may point to electron-rich alkaline earth layers. These should be highly polarisable, allowing them to facilitate uperconductivity by screening the repulsion between electrons and/or holes in the CuD layers.