| Abstract
| - The local structure and electronic properties of Mn in Na doped lanthanum manganites have been investigatedby means of Mn−K edge XAFS, at various temperatures ranging from RT to 30 K. The hole content dependson the amount of doping, both with Na which injects two holes per doping atom and with oxygennonstoichiometry. The holes are annihilated by oxygen under-stoichiometry via the formation of oxygenvacancies; the presence of a greater static disorder in the orthorhombic manganites is evidenced by bothEXAFS and XANES analysis. In the rombohedral samples, a single Mn−O distance is found. In addition,the trend of the EXAFS Debye−Waller factors for the Mn−O distance can be fitted with a simple Einsteinmodel, with no static disorder at low temperature. This evidence suggests small disorder of polaronic and ofJahn−Teller origin in the rombohedral samples at low temperatures, which is in contrast with what wasfound for the orthorhombic samples below Tc.
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