Abstract
Effects of oxygen content on the transport behavior of epitaxial La2/3Sr 1/3MnO $_{3-\delta}$ films on (110) NdGaO3 and (001) SrTiO3 substrates have been experimentally studied. A quantitative relation between the temperature of metal-to-insulator transition (T p ) and the content of oxygen vacancies is established, and it is found that oxygen non-stoichiometry causes a monotonic decrease of T p . A comparison to crystals La1-x Sr x MnO3 indicates that the reduction of hole concentration due to the incorporation of anionic vacancies dominates the variation of T p , while the vacancies themselves influence the detailed features of the T p - $\delta $ dependence. Strain in the film affects the effects of oxygen deficiency, and the metal-to-insulator transition disappears at a smaller $\delta $ value in tensily stressed films. In the temperature region above T p , oxygen vacancies affect the resistive behavior of the films mainly by modulating the content of Mn4 + . In contrast, extra effects due to the scattering of oxygen vacancies become important at low temperatures, causing an exponential increase of resistivity with $\delta $ . A further analysis indicates that oxygen deficiency enhances magnetic scattering, and leads to a resistivity upturn of the form $-\ln(T)$ when $\delta $ is significant.
Published Version
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