Compositional variation of magnetic properties in Ni71−xCoxAl29 alloys

The ferromagnetic shape memory alloys Ni71−xCoxAl29(x=35–39x=35–39) were studied through transport and magnetic investigations. The structural instability and the magnetic behaviour of the alloys were found to be extremely sensitive to the composition. All the compositions are ferromagnetic below room temperature and undergo martensitic transition in the temperature range between 100 and 270 K. The saturation moment, magneto-crystalline anisotropy constant, and the martensitic transition temperatures show a very interesting linear dependence on the cobalt concentration. The observed behaviour can be understood on the basis of increasing valence electron concentration when Ni is replaced by Co.