Martensitic and magnetic transformation in Ni–Mn–Ga–Co ferromagnetic shape memory alloys

The effect of Co addition on crystal structure, martensitic transformation, Curie temperature and compressive properties of Ni53−xMn25Ga22Cox alloys with the Co content up to 14 at.% was investigated. An abrupt decrease of martensitic transformation temperature was observed when the Co content exceeded 6 at.%, which can be attributed to the atomic disorder resulting from the Co addition. Substitution of Co for Ni proved efficient in increasing the Curie temperature. Compression experiments showed that the substitution of 4 at.% Co for Ni did not change the fracture strain, but lead to the increase in the compressive strength and the decrease in the yield stress. This study may offer experimental data for developing high performance ferromagnetic shape memory alloys.