AVS 49th International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI+SS-ThM

Paper MI+SS-ThM1
Photoemission and X-Ray Absorption Measurements on the CMR Materials La@sub 1-x@Ca@subx@MnO@sub3@ and La@sub 1-x@Sr@subx@MnO@sub3@

Thursday, November 7, 2002, 8:20 am, Room C-205

Session: Magnetic Spectroscopies
Presenter: N. Mannella, University of California at Davis
Authors: N. Mannella, University of California at Davis
A. Rosenhahn, Lawrence Berkeley National Laborarory
S. Mun, Intel Corporation
S.-H. Yang, IBM Almaden Research Center
Y. Tomioka, Joint Research Center for Atom Technology, Japan
Y. Tokura, Joint Research Center for Atom Technology, Japan
C.S. Fadley, Lawrence Berkeley National Laboratory
Correspondent: Click to Email
We report core and valence photoemission results obtained with synchrotron radiation for a set of high quality single-crystal CMR samples, namely La@sub 1-x@Ca@subx@MnO@sub3@ and La@sub 1-x@Sr@subx@MnO@sub3@ with x ranging from 0 to 0.4. The measurements were performed after cleaving the crystals in situ in UHV, yielding very clean and stoichiometric surfaces. X-ray absorption spectroscopy (XAS) and high-resolution valence band measurements at temperatures above and below the Curie temperature will also be discussed. The Mn 3s core level spectra show the expected multiplet splitting in binding energy, an effect which can sensitively probe the spin state of magnetic atoms. Our data reveal a non-linear dependence of the multiplet splitting on the hole concentration x, contrary to what one would expect in the simplest picture according to which hole doping causes a corresponding number of Mn@super 3+@ ions to become Mn@super4+@. These results may indicate an inadequacy of the conventional model based on the nominal Mn@super3+@ - Mn@super4+@ valence states. We have also measured Mn 3s spectra as a function of temperature. Our data suggest a short-range-order magnetic transition above the bulk Curie temperature, yielding a quantitative estimate of temperatures higher than T@subC@ at which the material shows magnetic order of local character. This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences Division, under Contract No. DE-AC03-76SF00098.