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MA: Magnetismus

MA 4: Magnetic Materials I

MA 4.7: Talk

Monday, March 27, 2006, 11:45–12:00, HSZ 401

Magnetic switching by twin boundary motion in NiMnGa shape memory ferromagnets — •Uwe Gaitzsch, Martin Pötschke, Stefan Roth, Bernd Rellinghaus, and Ludwig Schultz — IFW Dresden, P.O. Box 270116, 01171 Dresden

Magnetic shape memory materials gained a large research interest owing to their capability to deform by some percent via twin boundary motion under the influence of a magnetic field. Concurrently, they are supposed to react faster than conventional shape memory materials because neither heating nor cooling are involved. In our case off-stoichiometric Ni5Mn3Ga2 is used to produce a polycrystalline textured samples. Upon cooling this alloy transforms to a martensitic state at roughly 100^∘C. The evolving martensitic structure is either orthorhombic or tetragonal and depends on the thermomechanical history of the sample. Since only one of the two possible structures is suitable of providing the mandatory highly moblile twin boundaries, it is important to understand and control the phase formation process by appropriate thermal and mechanical treatment. Once the sample is given a suitable structure, samples for magnetomechanical testing are cut and investigated in magnetic fields of up to 0,8 T in compression tests. In this device the strain up to the crystallographic limit of reference samples could be determined.