Magnetostructural transition and magnetocaloric effect in Mn0.5Fe0.5NiSi1-xAlx melt-spun ribbons (x=0.055 and 0.060)

Melt-spun ribbons samples of the multicomponent alloy Mn0.5Fe0.5NiSi0.940Al0.060 were prepared and the magnetostructural transition (MST) and related magnetocaloric properties studied for as-solidified ribbons and ribbon samples annealed between 800 and 950 ? for 4 h. The results are compared with those reported in the literature for melt-spun ribbons with an Al content x = 0.055 and bulk alloys. It is shown that all samples undergo a first-order MST from a paramagnetic Ni2In-type hexagonal structure to a ferromagnetic TiNiSi-type orthorhombic one. Ribbons show broader isothermal entropy change delta S-T(T) curves with moderate maximum values of |delta S-T|(max) at 2 T (7.2-7.3 J kg(-1) K-1) in comparison with the reported for bulk alloys. However, the average value of the magnetic hysteresis loss linked to the hexagonal-to-orthorhombic transition is low in comparison with the one reported for most magnetocaloric materials with first-order magnetostructural transitions. This work underlines the effectiveness of this rapid solidification technique to produce highly homogeneous ribbon samples of multicomponent alloys.