Magnetic entropy change in Ni50.1Mn20.7Ga29.6 single crystal

Magnetic entropy change (DeltaS) of a single crystal Ni50.1Mn20.7Ga29.6 all oy under different applied fields has been investigated near the martensiti c-austenitic structural transition temperature of 219 K. With increasing ap plied field from 0.2 to 5 T, the sign of DeltaS changes from positive to ne gative. At 0.8 T the positive DeltaS reaches a maximum value of about 6.0 J /kg K, and above 0.8 T the increase of applied field results in a negative DeltaS. At 5 T DeltaS reaches -6.0 J/kg K. The interesting behavior of Delt aS is attributed to the first-order martensitic-austenitic structural trans ition at 219 K on heating. The phenomenon of the considerable magnetic entr opy change under the relatively low applied field of 0.8 T and the easy adj ustment of the martensitic-austenitic transition temperature indicate that Ni-Mn-Ga single crystal materials may have a possibility for practical appl ications as magnetic refrigerants. (C) 2001 American Institute of Physics.