Photoemission and X-Ray Absorption Measurements on the Cmr Materials La_1-xCa_xMnO3 and La_1-xSr_xMnO_3
Abstract
We report core and valence photoemission results obtained with synchrotron radiation for a set of high quality single-crystal CMR samples, namely La_1-xCa_xMnO3 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. In particular, Mn 3s core level spectra show the expected multiplet splitting in binding energy, a well-known effect in transition metal ions which can sensitively probe the exact 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 Mn3+ ions to become Mn4+. These results may indicate an inadequacy of the conventional model based on the nominal Mn3+ - Mn4+ valence states that is used to describe the transport properties of the manganites. Additional photoemission results from other core levels and valence levels, as well as x-ray absorption measurements, will also be discussed. 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.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2002
- Bibcode:
- 2002APS..MARG16002M