Polaronic correlations and phonon renormalization in L a1-x S rxMn O3 (x=0.2, 0.3)
Michael Maschek (Karlsruhe Institut für Technologie, TU Delft - RST/Fundamental Aspects of Materials and Energy)
J. P. Castellan (Karlsruhe Institut für Technologie, CEA-Saclay)
D. Lamago (Karlsruhe Institut für Technologie, CEA-Saclay)
D. Reznik (University of Colorado)
F Weber (Karlsruhe Institut für Technologie)
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Abstract
According to standard theory the magnetoresistance magnitude in ferromagnetic manganites crucially depends on the electron-phonon coupling strength. We showed that in La0.7Sr0.3MnO3 the phonon renormalization is strong, despite its relatively small magnetoresistance. Here, we report results of a similar inelastic neutron-scattering investigation of a closely related compound, La0.8Sr0.2MnO3, where the magnetoresistance is enhanced. We find similar phonon renormalization and dynamic CE-type polaron correlations as in La0.7Sr0.3MnO3. However, quantitative comparison of the results for the two samples shows that only polaron lifetime is well correlated with the strength of the colossal magnetoresistance.