Dresden 2011 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 19: Poster I (Bio- and Molecular Magnetism/ Magnetic Particles and Clusters/ Micro- and Nanostructured Magnetic Materials/ Magnetic Materials/ Multiferroics/ Magnetic Shape Memory Alloys/ Electron Theory of Magntism/ Spincaloric Transport/ Magnetic Coupling and Exchange Bias/ Magnetization Dynamics/ Micromagnetism and Computational Magnetics)

MA 19.63: Poster

Dienstag, 15. März 2011, 10:45–13:00, P2

Magnetic domain structure evolution in NiMnGa magnetic shape memory alloy — •Andreas Neudert and Jeffrey McCord — Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstr. 400, 01328 Dresden

We have investigated the magnetic domain structure evolution due to twin boundary motion in single crystalline NiMnGa (10M) magnetic shape memory samples. Due to the high mobility of the twin boundaries they can be moved by applying a magnetic field or mechanical stress. In general, the equilibrium domain width in magnetic samples depends on the interplay of demagnetization and anisotropy energy. Depending on the orientation of the easy axis within a magnetic sample different equilibrium widths can be found. We investigated the magnetic domain structure using optical polarization microscopy and magnetic indicator film technique. We found that the qualitative domain structure depends on whether the sample was subjected to magnetic fields or mechanical stresses. In both cases the twin boundary is moved and therefore the orientation of the magnetic easy axis is changing. During the field induced motion the variants are partially saturated, whereas during the stress induced motion the net magnetization in the variants is unchanged. This results in a completely different remagnetization process and magnetic domain structure. Using domain theory the equilibrium domain width can be calculated and is compared with the experimental values. We greatly acknowledge support by DFG priority program SPP 1239.