Magneto-structural transition and magnetocaloric effect of melt spinning Ni₅₀Mn₂₉Ga_21-xTb_x (x = 0-1) ribbons

Ni₅₀Mn₂₉Ga_21-xTb_x (x=0-1) ribbons with the solid solution of Tb element were synthesized by the melt spinning method. The phase transformation, magnetic properties and magnetocaloric effect were investigated. With the increasing Tb content the martensitic transformation temperatures were gradually increased while the Curie temperature was monotonously decreased. According to the detected phase transition temperatures, a phase diagram was established to describe the dependence of the magneto-structural transition on the Tb content. Three types of magneto-structural transitions were observed. Especially, the martensitic transformation was coincided with the magnetic transition in the single phase alloy with x = 0.1, giving rise to the coupled magneto-structural transition from ferromagnetic martensite to paramagnetic austenite. Sizable magnetic entropy change of 4.31 J/Kg K was induced from the coupled magneto-structural transition by the application of magnetic field of 50 kOe at 349.5 K.