Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 17: Magnetic Shape Memory Alloys

MA 17.4: Vortrag

Mittwoch, 28. März 2007, 16:00–16:15, H10

Investigation of structure and microstructure transformations of Ni-Mn-Ga single crystal exhibiting magnetic shape memory effect by neutron diffraction — •Heczko Oleg^{1, 3} and Prokes Karel² — ¹IFW Dresden,Helmholtzstrasse 20, 01069 Dresden, Germany — ²Berlin Neutron Scattering Center, Hahn-Meitner-Institut Berlin, Glienicker Straße 100, D-14109 Berlin (Wannsee), Germany — ³Laboratory of Materials Science, Helsinki University of Technology, Vuorimiehentie 2A, P.O. Box 6200, FI-02015 TKK, Espoo, Finland

Neutron diffraction of single crystal of alloy Ni_49.7Mn_29.3Ga₂₁ exhibiting 6% MSM effect was carried out in HMI, Berlin. The single crystal was mounted into cryostat with one of 100 directions along the magnetic field and perpendicular to diffraction plane. The set of nuclear Bragg reflections was recorded by 2D position sensitive detector after zero-field cooling and cooling in 5T magnetic field at different temperatures above and below martensitic transformation temperatures. The martensitic variants distribution and quality and inhomogeneity of the single crystal were studied using ω scan. Using measurement in reciprocal space we recorded a set of reflections that appear due to structural modulation (5M) of the martensite, however, the set seems to be incomplete with missing or very weak reflections of second order compared with X-ray diffraction. No sharp magnetic reflection of suggested antiferromagnetic ordering of excess Mn was observed.