  We report on a novel class of nanocrystalline/amorphous
Gd$_3$Ni/Gd$_{65}$Ni$_{35}$ composite microwires, which was created directly by
melt-extraction through controlled solidification. X-ray diffraction (XRD) and
transmission electron microscopy (TEM) confirmed the formation of a biphase
nanocrystalline/amorphous structure in these wires. Magnetic and magnetocaloric
experiments indicate the large magnetic entropy change (-$\Delta$SM ~9.64 J/kg
K) and the large refrigerant capacity (RC ~742.1 J/kg) around the Curie
temperature of ~120 K for a field change of 5 T. These values are ~1.5 times
larger relative to its bulk counterpart, and are superior to other candidate
materials being considered for active magnetic refrigeration in the liquid
nitrogen temperature range.
