Large cryogenic magnetocaloric effect of DyCo2 nanoparticles without encapsulation

The structure and formation of nanoparticles without encapsulation of the intermetallic compound DyCo2 were investigated by using x-ray diffraction and high-resolution transmission electron microscopy. The DyCo2 nanoparticles are stable in air without any shell protection. A large magnetic-entropy change of 13.2 J kg(-1) K-1 was found at 7.5 K in an applied-field change from 1 to 7 T, which is ascribed to the large magnetic moment density and the weak interaction energy in the nanoparticles. Such oxidation-resistant rare-earth transition-metal compound nanoparticles with large cryogenic magnetocaloric effect are useful for refrigeration applications at low temperatures. (c) 2008 American Institute of Physics.