Ni-Mn-Ga-(Co, Fe, Cu) high temperature ferromagnetic shape memory alloys: Effect of Mn and Ga replacement by Cu

Abstract We have studied a tailoring effect of Mn or Ga replacement by Cu in two Ni43Co7Mn20-xFe2Ga21Cu7+x (x = 0.25, 0.5, 0.75, and 1.0 at. %) and Ni43Co7Mn20Fe2Ga21-xCu7+x (x = 0.5, 1 and 1.5 at. %) magnetic shape memory alloys with non-modulated tetragonal martensite, to increase the magnetic actuation temperature. A direct correlation between tetragonality ratio (c/a) and the martensitic (MT) and Curie temperatures (TC) has been disclosed in both alloys series. Some of the studied alloys show a combination of high MT temperature (>370 K) and TC (>430 K), which extends the reported composition range of high temperature ferromagnetic shape memory alloys.