Strong oxygen-isotope effect on the intrinsic resistivity in the ferromagnetic state of manganites
Abstract
Oxygen-isotope effects on the intrinsic resistivity have been studied in high-quality epitaxial thin films of La 0.75 Ca 0.25 MnO 3 and Nd 0.7 Sr 0.3 MnO 3. We found that the residual resistivity o increases by about 15͑3͒% upon replacing 16 O by 18 O. Furthermore, the temperature dependent part of the resistivity at low temperatures consists of an AT 4.5 term contributed from two-magnon scattering, and a B s /sinh 2 (ប s /2k B T) term which arises from scattering by a soft optical phonon mode. The absolute magnitudes of the coefficient A and the phonon energy ប s for both isotope samples are in quantitative agreement with theoretical predictions.
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