Regensburg 2007 – scientific programme

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MA: Fachverband Magnetismus

MA 22: FV intern Symposium: "Heusler Alloys"
Invited Talks Kübler/Yamamoto/Inomata/Silvia Picozzi

MA 22.6: Talk

Thursday, March 29, 2007, 12:30–12:45, H10

Structural characterization of Heusler compounds using NMR — •Sabine Wurmehl¹, Marek Wojcik², Gerhard Fecher¹, Benjamin Balke¹, Vadim Ksenofontov¹, Verena Jung¹, and Claudia Felser¹ — ¹Johannes Gutenberg - Universität, 55099 Mainz, Germany — ²Institute of Physics, Polish Academy of Sciences, 02-668 Warszawa, Poland

The L2₁ ordered Heusler alloys Co₂Mn_1−xFe_xSi with 0 ≤ x ≤ 1 attracted much scientific interest, as they are predicted to show high spin polarisation at the Fermi-energy.

Therefore Co₂Mn_1−xFe_xSi samples were investigated using spin echo nuclear magnetic resonance (NMR) measurements. This method provides a tool to measure the hyperfine fields. The hyperfine fields represent a very sensitive local probe to order-disorder phenomena.

The NMR measurements of polycrystalline Co₂FeSi samples exhibit a two-peak spectrum with an additional shoulder. This additional signals are attributed to second-order quadrupole splitting, a so called asymmetric line broadening and might be caused by tension within the structure (strain). This effect occurs even in highly ordered systems. Thus previous structural results are corroborated, demonstrating even locally a very high degree of order in Co₂FeSi.

The NMR spectra of the series Co₂Mn_1−xFe_xSi ((0.1≤ x ≤0.9) exhibit multiplet structures. These might be explained by quadrupole splitting and statistical distribution of Mn and Fe atoms on the Mn site. In summary, the high degree of order in Co₂Mn_1−xFe_xSi is shown.

(This work is funded by the DFG in FG 559.)