Berlin 2008 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

MA: Fachverband Magnetismus

MA 14: Magnetic Half Metals and Oxides

MA 14.5: Vortrag

Dienstag, 26. Februar 2008, 11:30–11:45, EB 202

Solving the problem of structure determination in 3d transition metal based Heusler compounds. — •Benjamin Balke, Gerhard H. Fecher, Christian Blum, Lubna Basit, and Claudia Felser — Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg - University, 55099 Mainz

This work reports on the structural investigation of Fe-containing, Co2-based Heusler compounds (Co₂FeZ with Z = Al, Si, Ga, Ge) using anomalous X-ray diffraction (XRD) and extended X-ray absorption fine structure spectroscopy (EXAFS). Using XRD, it was shown that Co₂FeAl crystallizes in the B2 structure whereas Co₂FeSi crystallizes in the L2₁ structure. For compounds containing Ga or Ge, the XRD technique with regular laboratory sources for excitation can not be used easily to distinguish the two structures. For this reason, EXAFS was used to elucidate the structure of these two compounds. The absorption experiments close to the K-edges of Co, Fe, Ga, and Ge indicated that both compounds crystallize in the L2₁ structure. Exciting the XRD at the K-edges of Co and Fe leads to anomalous X-ray scattering. The dependence of the scattering parameters on the energy close to the absorption edges was used to identify the L2₁ structure of the Ga and Ge containing compounds unambiguously. The applicability of the techniques on nano-scaled materials will be demonstrated for the example of Co₂FeGa nano-particles with sizes of below 25 nm.

The authors gratefully acknowledge financial support by the DfG (Research Unit 559).