STUDY OF STRUCTURE, MAGNETIC AND MAGNETOCALORIC PROPORTIES IN Ni_(45)Co_5Mn_(38)Sb_(12) HEUSLER SYSTEM

摘要

Considerably large martensitic transition temperature has been observed after substituting Co for Ni site in Ni_(45)Co_5Mn_(38)Sb_(12) system. This system exhibits austenite L2_1 cubic structure with a=5.96 A° at high temperatures, while it has orthorhombic structure in the martensitic phase. From the M(T) plots it is found that with Co substitution, the austenite phase get stabilized and hence the martensitic transition shifts to lower temperature. The magnetic entropy change of 34 J/kg K is found to be in a field of 50 kOe in martensitic transition region. In Ni_(45)Co_5Mn_(38)Sb_(12) system, from temperature variation of neutron diffraction data has shown that with increase in temperature the cell volume increases. Near the martensitic transition from orthorhombic to cubic phase transition there is sudden increase of 0.3% of cell volume established as well as hysteresis appear in between heating and cooling curve for Ni_(45)Co_5Mn_(38)Sb_(12) system.