Temperature dependence of magnetic properties in Ni-Mn-Ga shape memory alloys

Abstract

Due to exhibiting giant field-induce strain, the Ni2MnGa shape memory alloys are great interest for both scientific researches and industry applications. The non-stoichiometric Ni50Mn25+xGa25-x alloys with x varied from 1.5, 2.5 to 4 have been fabricated by arc-melting. Martensitic transformation temperature for structure transformation from tetragonal to cubic (T-M) was observed from the magnetization, electrical resistivity and X-ray diffraction studies as functions of temperature below 400 K. We found that T-M increases roughly from 280 K to 310K with increasing x from 1.5 to 4. However, the Curie transition (T-M) is roughly at 380 K for all the samples, it is insensitive to the variation of Mn/Ga ratio. The electrical resistivity data exhibit a deep near T-M and a slope change near T-C. We have experimentally demonstrated that the shape memory effect can be occurred at room temperature with a proper concentration variation of Mn and Ga. (C) 2004 WILEYNCH Verlag GmbH & Co. KGaA, Weinheim.