J. Phys. IV France 11 (2001) Pr8-251-Pr8-255
An exploration on magneto-shape memory effect in a Co-Ni single crystalB. Jiang, Y. Liu, W. Zhou and X. Qi
Open Laboratory of Education, Ministry for High-Temperature Materials and Testing, Shanghai Jiao Tong University, Shanghai 200030, China
A Co-33%Ni (in mass) single crystal was grown by floating zone method in argon gas. The intrinsic magnetic properties, martensitic and austenitic transformation temperatures and Curie point of the crystal both in  and  directions were determined by the vibrating sample magnetometer (VSM) and magnetization balance (MB). The magnetic-field-induced strains were measured by strain gauges through the KJC magnetic measuring system. In  direction, the as-grown single crystal exhibits a high saturation magnetization of 124 Am2.kg-1, which is nearly doubled compared with that of Ni2MnGa. A reversible strain of 3% was induced by an applied pulse niagnetic field of 2 T along  direction at a temperature (180K) in the range between Ms and Md, that is ten times more than that of Ni2MnGa. While applying the pulsed magnetic field at temperatures below Ms (such as 155K and 145K), a recoverable field induced strain of 1% was obtained and about 0.5% strain was retained. After heating to room temperature, about 60% whole strain was recovered. If applying magnetic field along  direction of the crystal, no visible strain could be induced. According to the martensitic transformation theory on FCC to HCP structure, a mechanism based on the movement of a/6<112> partial dislocations driven by an applied magnetic field is presented.
© EDP Sciences 2001