Low field giant magnetocaloric effect in RNiBC (R = Er and Gd) and enhanced refrigerant capacity in its composite materials

The magnetic properties and magnetocaloric effect (MCE) in RNiBC (R = Er and Gd) compounds and its composite materials were investigated. A giant low field reversible MCE was observed in RNiBC compounds at 5 and 13 K for R = Er and Gd, respectively. Under a relative low field change of 2 T, the maximum values of magnetic entropy change (-Delta S-M(max)) reach 17.1 and 9.3 J/kg K for R = Er and Gd, respectively. A table-like MCE in the temperature of 4-20 K and enhanced refrigerant capacity (RC) were found in the ErNiBC-GdNiBC composite materials. For the magnetic field changes of 1 T and 2 T, the maximum improvement of RC reach 31% (19%) and 30% (8%), in comparison with that of individual compound ErNiBC (GdNiBC), respectively. The excellent MCE properties make the RNiBC composite materials attractive for low temperature magnetic refrigeration. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752738]