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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 Felser11Johannes Gutenberg - Universität, 55099 Mainz, Germany — 2Institute of Physics, Polish Academy of Sciences, 02-668 Warszawa, Poland

The L21 ordered Heusler alloys Co2Mn1−xFexSi with 0 ≤ x ≤ 1 attracted much scientific interest, as they are predicted to show high spin polarisation at the Fermi-energy.

Therefore Co2Mn1−xFexSi 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 Co2Mn1−xFexSi ((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 Co2Mn1−xFexSi is shown.

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

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