Effect of ball milling and thermal treatment on exchange bias and magnetocaloric properties of Ni_(48)Mn_(39.5)Sn_(10.5)Al_2 ribbons

摘要

The combined effect of ball milling and subsequent heat treatment on microstructure, magnetic, magnetocaloric and exchange bias properties of Ni_(48)Mn_(39.5)Sn_(10.5)Al_2 ribbons is reported. The annealing treatment results in the increase of the critical martensitic transformation temperature. The magnetic entropy change ΔS_M of the order of 7.9 and -2.3 J kg K~(-1) for the annealed 50-32 μm powder fraction is determined. This is less than in the as melt spun ribbon but appears at a considerably higher temperature. At the same time EB is decreased due to annealing treatment This decrease is attributed to the strengthened ferromagnetic exchange coupling due heat induced stress and structural relaxation.