Magnetic and Microstructure Properties of Co-doped rapidly solidified Ni₅₀Mn_25-xCo_xGa₂₅ Heusler alloys

Cobalt-doped melt-spun ribbons of Ni₅₀Mn_25-xCo_xGa₂₅ were prepared to study the influence of cobalt on the magnetic properties of the NiMnGa based Heusler alloy. Bulk specimens were also prepared for a comparative study. The bulk specimens and the melt spun ribbons were annealed at 900 deg. C for 5 hours followed by quenching. Microstructural studies revealed an extensively twinned structure which is beneficial for magnetic field induced strain. The magnetization measurements showed a reduction in the moment with an increase in the cobalt content from 78.4 emu/g to 52.7 emu/g for Co (x=6) and Co (x=10), respectively. A reduction was also observed in the T_C when cobalt content was increased from Co (x=6) (T_C =386K) to Co (x=10) (T_C =263K).