Berlin 2008 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 36: Phase Transitions II

MM 36.5: Vortrag

Donnerstag, 28. Februar 2008, 12:45–13:00, H 0107

The study on the structure, magnetism and shape memory effect of the ferromagnetic shape memory alloy CoNiGa. — •Xuefang Dai and Claudia Felser — Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg - University, 55099 Mainz

The structure, magnetic properties and shape memory effect of CoNiGa alloys were investigated in the bulk, as-spun and single crystal samples. It was found by experiments that the ternary CoNiGa alloys have good shape memory effect, and the shape memory strain can be easily controlled by temperature, magnetic field and stress. For optimizing the mechanical properties, the iron was doped in the CoNiGa alloys. Excellent superelasticity was obtained in the quaternary CoNiFeGa single crystal samples. The superelastic strain of 6.7% can be induced by compressed stress and 11% can be obtained in tension test. In addition, the perfect superelasticities also showed up in bending and torsion tests. Special CoNiFeGa crystals with regular defects have also been grown in a deep super-cooling condition. These defects result in a large energy barrier which leads to a very sharp martensitic transformation within a temperature window of only 2 K. On the other hand, we also prepared Si-doped CoNiGa alloys, which exhibit larger magnetic-field-induced strain than the ternary CoNiGa alloys. This improvement in magnetic-field-induced strain can be attributed to the increase of the magnetic anisotropy induced by the Si-dopant.

Xuefang Dai acknowledges the support by the Institute of Physics, Chinese Academy of Sciences, Beijing 100080.