Berlin 2005 – wissenschaftliches Programm

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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

Montag, 7. März 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 Co₂Cr_1−xFe_xAl 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.)