Hard X-ray photoemission study of Mn 2p core-levels of La1-xSrxMnO3 thin films

In order to clarify the intrinsic bulk electronic structure of La1-xSrxMnO3 (LSMO) thin films, we have performed high-energy (hν=5.95-bar keV) synchrotron photoemission spectroscopy (PES) of Mn 2p core-levels. In sharp contrast with the previous soft X-ray PES (hν=800-1486.6-bar eV), the high-energy PES spectra exhibit a clear additional peak at the low binding-energy side of the Mn 2p3/2 peak. To check for surface sensitivity, we measured take-off-angle dependence of Mn 2p core-levels. The results indicate that this additional peak originates from the bulk electronic structure. The peak shows a noticeable increase in the metallic phase of LSMO for x=0.2 and 0.4, indicating that the origin of this peak is strongly related to the metallic physical properties of LSMO thin films. A single ion (MO6) cluster calculation including charge transfer from doping-induced states reproduces the new bulk-derived feature observed in Mn 2p core-levels