Local structure and electronic properties of the rhombohedral and orthorhombic colossally magnetoresistive manganites La1-xNaxMnO3 by Mn-K edge EXAFS and XANES.
The local structure and electronic properties of Mn in Na doped lanthanum manganites have been investigated by means of Mn-K edge XAFS, at various temperatures ranging from RT to 30 K. The hole content depends on the amount of doping, both with Na which injects two holes per doping atom and with oxygen nonstoichiometry. The holes are annihilated by oxygen under-stoichiometry via the formation of oxygen vacancies; the presence of a greater static disorder in the orthorhombic manganites is evidenced by both EXAFS 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 Einstein model, with no static disorder at low temperature. This evidence suggests small disorder of polaronic and of Jahn-Teller origin in the rombohedral samples at low temperatures, which is in contrast with what was found for the orthorhombic samples below T(c).
Ghigna
Paolo
P
Dipartimento di Chimica Fisica M. Rolla, IENI/CNR and INSTM, Università di Pavia, V.le Taramelli 16, I-27100, Pavia, Italy.
Carollo
Arianna
A
Flor
Giorgio
G
Malavasi
Lorenzo
L
Peruga
Gloria Subias
GS