Magnetostructural transitions in Mn-rich Heusler Mn-Ni-In melt-spun ribbons with enhanced magnetocaloric effect

The magnetostructural transition behavior and magnetocaloric effect of Mn-rich Heusler Mn-Ni-In melt-spun ribbons have been investigated in the present study. Experimental results showed that the martensitic transition temperatures decreased by substituting small amounts of Ni with Mn in Mn49+xNi42−xIn9 (x=0,1,2). Within a temperature range from 100 K to 380 K, the Mn49Ni41In9 underwent a martensitic transformation from a paramagnetic L21-type cubic austenite to a ferromagnetic modulated fourteen-layered monoclinic (14M) martensite, followed with a ferromagnetic→weak-magnetic transition in martensite upon cooling. While for both Mn50Ni41In9 and Mn51Ni40In9, the paramagnetic→ferromagnetic transition in austenite occurred prior to the martensitic transformation upon cooling. Under a magnetic field change of 30 kOe, the maximum magnetic entropy changes of the Mn50Ni41In9 melt-spun ribbons were found to be 5.7 J/kg K and −2.3 J/kg K in the vicinity of martensitic transformation and magnetic transition of austenite, respectively. An enhanced total effective refrigeration capacity as high as 184.2 J/kg was obtained in the Mn50Ni41In9 melt-spun ribbons.