In situ resonant photoemission characterization of La0.6Sr0.4MnO3 layers buried in insulating perovskite oxides

We have investigated the Mn 3d partial density of states in SrTiO3(STO)/La0.6Sr0.4MnO3(LSMO) heterointerfaces as well as of LSMO films using Mn 2p-3d resonant photoemission spectroscopy. The strong enhancement of the Mn 3d spectra at the Mn 2p-3d threshold enables us to extract the Mn 3d spectra of LSMO layers in the vicinity of the interface with the STO overlayers. We have found that the spectral intensity of e(g up arrow) states near the Fermi level is drastically reduced when the LSMO film is capped with STO overlayers. The close similarity in reduction of the intensity of the e(g up arrow) states between the STO/LSMO interface and hole-doped LSMO films suggests that the hole doping into the LSMO layer close to the STO layer originates from the chemical carrier-concentration modulation at the valence-mismatched interface composed of the stacking sequence -TiO2-SrO-MnO2-La0.6Sr0.4O-, which is inevitable for multilayers based on perovskite oxides. (C) 2006 American Institute of Physics.