Dresden 2003 – wissenschaftliches Programm
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MA: Magnetismus
MA 3: Magnetische Materialien
MA 3.6: Vortrag
Montag, 24. März 2003, 11:30–11:45, HSZ/401
Magnetic shape memory effect in Ni-Mn-Ga and Ni-Mn-Al — •Mehmet Acet1, Eyüp Duman1, Eberhard F. Wassermann1, Llouis Mañosa2, and Antoni Planes2 — 1Tieftemperaturphysik, Gerhard-Mercator-Universität, 47048 Duisburg — 2Departament d′Estructura i Constituents de la Matèria, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, 08028 Barcelona Catalonia, Spain
The Heusler compound Ni2MnGa undergoes a structural transition from the L21 parent phase to the tetragonal B′ martensitic phase near room temperature. The magnetic ordering in both parent and product phases are ferromagnetic, and in the martensitic phase, the application of an external magnetic field of about 1 T can induce strains as large as about 10% in single crystals. Such material are known as magnetic shape memory alloys. The Heusler compound Ni2MnAl also undergoes a martensitic transformation at off-stoichiometric compositions. However, the parent phase is either B2 or a mixture of B2 and L21 due to the significantly lowered B2-L21 ordering temperature compared to that of Ni2MnGa. Despite the mixed nature of the parent phase in off-stoichiometric Ni2MnAl, it is possible to extract information on field induced strains in the martensitic phase of Ni2MnAl. From low field magnetization measurements on off-stoichiometric Ni2MnAl, we show that the nature of the field induced strains are similar to those in Ni2MnGa and that the presence of a single L21 parent phase is essential for inducing large strains in the martensitic state.