Berlin 2005 – scientific programme
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MA: Magnetismus
MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65
MA 20.140: Poster
Monday, March 7, 2005, 14:00–18:00, Poster TU C
EXAFS-measurements on doped Heusler compounds — •Sabine Wurmehl1, Gerhard H. Fecher1, Jonder Morais2, Maria C. M. Alves2, Sergio R. Teixeira2, Claudia Felser1, and Gerd Schönhense1 — 1Johannes Gutenberg - Universität, 55099 Mainz, Germany — 2Universidade Federal do Rio Grande do Sul, Porto Alegre, 91501-970 RS, Brazil
Doped Heusler compounds with composition Co2Cr1−xFexAl were prepared by arc melting and comprehensively characterized by means of SQUID magnetometry, Mößbauer spectroscopy, ESCA and AES depth profiling. X-ray diffraction pointed on structural disorder phenomena. Therefore, EXAFS measurements on polished discs and powders were performed. The XAS spectra were taken at the 3d-metal K-edges to compare each edge of the contributing d-metals in powder and bulk samples. The near edge region (NEXAFS) is similar for each edge and gives no hint for chemical alteration. The EXAFS signal of Cr and Co in the same composition differs significantly if the measurements were taken from powder or polished discs. This shows that the neighborhood of Fe is not changed when grinding a sample, whereas Cr and Co exhibit different surroundings in powder and bulk material. It indicates that determining structural properties from powder diffraction may lead to wrong conclusions.
(This work is funded by the DFG in FG 559.)