J. Phys. IV France 112 (2003) 955
10% magnetic-field-induced strain in Ni-Mn-Ga seven-layered martensiteA. Sozinov1, A.A. Likhachev2, N. Lanska2, K. Ullakko2 and V.K. Lindroos1
1 Helsinki University of Technology, Laboratory of Physical Metallurgy and Materials Science, P.O. Box 6200, 02015 Hut, Finland
2 Helsinki University of Technology, Laboratory of Biomedical Engineering, P.O. Box 2200, 02015 Hut, Finland
Magnetic-field-induced strain of approximately 10% is reported in Ni 48.8Mn 29.7Ga 21.5 alloy at ambient temperature in a magnetic field of the order of 1 T. It was confirmed by different experimental methods that the strain is contributed by twin boundary motion. The crystal structure of thermally-induced martensitic phase in this alloy was found to be close to orthorhombic one in temperature range from 245 K to 333 K. The lattice parameters are a=0. 619 nm, b=0.580 nm, c=0.553 nm (relating to the cubic parent phase coordinates) at ambient temperature. Detailed x-ray study revealed seven-layer modulation along the (110) [ 1 0] , system. The results of mechanical tests and magnetic anisotropy property measurements are also reported. The necessary conditions for the observation of a giant magnetic field-induced strain in non-stoichiometric Ni 2MnGa alloys based on the new experimental data are discussed.
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