材料期刊网

The HoCo(2) nanoparticles are found to be stable in air without any shell protection. The HoCo(2) nanoparticles display superparamagnetic properties between their blocking temperature of 40 K and Curie temperature of 78 K. The magnetic-entropy change increases with decreasing temperature at a certain magnetic-field change, which is ascribed to the competition between the Zeeman energy and thermal-agitation energy at low temperatures. A large magnetic-entropy change of 19.4 J kg(-1) K(-1) was found at 7.5 K in an applied-field change from 1 to 7 T, while 6.1 J kg(-1) K(-1) was achieved in a low field change of 1 T. HoCo(2) nanoparticles are useful for application of magnetic refrigeration at low temperatures.