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Regensburg 2016 – scientific programme

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MA: Fachverband Magnetismus

MA 17: Poster Session I

MA 17.64: Poster

Tuesday, March 8, 2016, 09:30–12:30, Poster B1

Understanding the ordering phenomena in Co2FeAl0.5Si0.5 through in situ neutron diffraction — •Ahmad Omar1, Matthias Frontzek2, Alexey Alfonsov1, Bernd Büchner1,3, and Sabine Wurmehl1,31IFW Dresden, 01069, Germany — 2Paul Scherrer Institute, 5232 Villigen, Switzerland — 3Institut für Festkörperphysik, TU Dresden, 01062, Germany

The Co2FeAl0.5Si0.5 Heusler compound is predicted to be a half-metallic ferromagnet in the ordered L21 structure but it is difficult to obtain a pure L21 order due to anti-site disorder. Hence, 100% spin polarization has not been observed in general. Therefore, it is important to understand the ordering phenomena with temperature in the material so as to optimize the ordering post-synthesis. We present in situ neutron diffraction measurements performed during high temperature annealing of powder samples along with powder neutron diffraction at room temperature on pre-annealed polycrystalline samples in order to compare the effect of various annealing procedures. We show that the annealing procedures commonly followed in literature do not offer significantly large improvement in the L21 order. A sharp L21-B2 ordering transition is not observed, in contrast to what is commonly understood. We also discuss the ordering phenomena in the light of existence and evolution of antiphase domains and domain boundaries though detailed line profile analysis of the neutron diffraction data. Based on our understanding, we have been able to optimize the annealing procedure. A higher L21 ordering, as compared to conventional annealing, has been obtained which was confirmed using zero-field NMR measurements.

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