Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 10: Magnetic Materials

MA 10.9: Vortrag

Montag, 25. Februar 2008, 17:15–17:30, H 1028

Mößbauer spectroscopy of Co₂Mn_1−xFe_xAl. — •Verena Jung, Gerhard H. Fecher, Benjamin Balke, Vadim Ksenofontov, and Claudia Felser — Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg - University, 55099 Mainz

Heusler compounds have been recognized as suitable materials for magneto-electronics. The Co₂ based compounds are of special interest for applications as they exhibit a wide range of magnetic properties and Curie temperatures up to 1100 K. In this work solid solutions of Co₂Mn_1−xFe_xAl with x = 0, 0.1,…, 1 were prepared by arc melting and annealed for 7 days at 800^∘C. The structure was characterized by XRD and a single B2 phase was found over the entire range of compositions. The magnetic properties were measured with a SQUID magnetometer revealing that the moments are higher than expected for half-metallic ferromagnetism. The local environment and hyperfine magnetic fields of the iron atoms were studied by ⁵⁷Fe Mößbauer spectroscopy in transmission geometry at room temperature for Co₂Mn_1−xFe_xAl samples with x=0.2…1. The obtained spectra are explained by hyperfine magnetic field distributions implying 7 contributions with different values and line widths in agreement with the local structure in the cubic lattice. A shift of the relative intensities of the seven hyperfine magnetic fields is explained by the appearance of an additional ordered portion with L2₁ structure for samples with Fe concentrations of x>0.7 not being detected by XRD.

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