Magnetocaloric effect in melt-spun nickel based Heusler alloys

Abstract

Dwindling energy resources and unsustainable energy consumption are increasingly being seen as major global problems. Hence, energy efficient cooling technology has become an important research topic. Magnetic refrigeration, based on the magnetocaloric effect (MCE), has significant advantages compared to conventional gas compression cooling techniques, e.g., no green house gases as well as high energy efficiency. Because of these significant advantages, magnetic refrigeration has attracted considerable attention as an alternative to conventional refrigeration. Gadolinium, which is usually chosen as the magnetocaloric material (MCM), is very expensive, hence we focused on developing a cheaper MCM, i.e, Ni-Mn-Sn base alloys with attractive magnetic properties.

The martensitic transition and the magnetic entropy change of Ni50Mn50-xSnx (x=6, 9, 11, 13, 15, 17, 20), Ni50-yCoyMn37Sn13 (y=0.5, 1.5, 1.7, 2.5, 5) and Ni50-zCozMn38Sn12 (z=1, 1.4, 2) Heusler alloys were studied. Synthesis by melt spinning, characterization and magnetic property measurements were carried out. The Ni-Co-Mn-Sn alloys studied in this work exhibited an entropy change (ΔS) of ~32 J.kg-1.K-1 at 50 kOe, which is much larger than the corresponding value for the “giant” magnetocaloric Ni50Mn37Sn13 alloys. Co additions result in a lowering of the martensitic transition temperature without significant loss in ΔS. Therefore, a wide range of service temperatures can be achieved, making these alloys attractive candidates for room temperature cooling applications.