Abstract

The thermal dependence of the magnetic entropy change (Delta S-M(T)) and refrigerant capacity (RC) of austenite in as-quenched ribbons of chemical composition Ni51.1Mn31.2In17.7 produced by melt spinning at a high cooling rate of 48 ms(-1) is reported. The effect of annealing at 1073 K on the structure and the magnetic properties was studied. The as-quenched sample is a single-phase austenite that presents a B2 ordered structure. The annealing on the melt spun samples produced a L2(1)-type ordered structure. Austenite is characterized by a broad Delta S-M(T) curve that, for a field change of 5.0 T, exhibits a full-width at half-maximum delta T-FMHW of 107 K, a peak value of the magnetic entropy change Delta S-M(peak) of -3.1 Jkg(-1) K-1, and RC = 345 Jkg(-1). Although annealed samples show larger Delta S-M(peak) values the narrower Delta S-M(T) curves leads to a reduction in RC. Thus, the as-quenched sample shows a higher efficiency for a refrigerant cycle. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3676606]