Dresden 2006 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 4: Thin film analysis II

DS 4.1: Vortrag

Montag, 27. März 2006, 11:15–11:30, GER 38

Determination of Mn valency using ELNES in the (S)TEM — •Thomas Riedl, Thomas Gemming, and Klaus Wetzig — IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany

The analysis of electron energy-loss near-edge structures (ELNES) in the (S)TEM provides a tool to probe the symmetry-projected density of unoccupied states near the Fermi level at high spatial resolution. In particular, the Mn-L_2,3 and O-K edges undergo characteristic changes with Mn valency. With increasing Mn valency the white-line intensity ratio I(L₃)/I(L₂) decreases and the energy separations between (a) Mn-L₃ and O-K_a and (b) O-K_b and O-K_a increase [1]. Our ELNES measurements of La_1−xSr_xMnO₃ (x=0.2, 0.4) manganites indicate that the Mn valence sensitivity of both energy separations exceeds that of I(L₃)/I(L₂) by a factor of ≈2. With respect to the impact of oxidation states on the performance of magnetoelectronic devices based on manganite thin films the mentioned Mn valence-sensitive ELNES quantities have been investigated at the La_1−xSr_xMnO₃ /SrTiO₃ interface. Preliminary results point to a reduction of the Mn valency close to the interface [2].

[1] J. H. Rask et al.: Ultramicr. 21 (1987) 321

[2] We acknowledge the DFG for financial support via FOR 520, project GE 1037/8.