Magnetic entropy change and its temperature variation in compounds La(Fe1-xCox)11.2Si1.8

Magnetic entropy change DeltaS of compounds La(Fe1-xCox)(11.2)Si-1.8 with the cubic NaZn13-type structure was investigated around their Curie temperature T-C. It is found that the phase transition is completely reversible, indicating a nature of second order phase transition. The maximum value of \DeltaS\similar to13.0 J/kg K under a field of 5 T was achieved in compound LaFe11.2Si1.8 at its T-C of similar to222 K, which exceeds that of most materials involving a second order transition at the corresponding temperature. With increasing substitution of Co for Fe from x=0 to x=0.8, T-C shifts from 222 to 307 K and entropy change decreases. However, \DeltaS\ still has a considerable magnitude near room temperature. The large magnetic entropy change is believed to be due to the abrupt change of magnetization at T-C, which is associated with the strong structural and magnetic interplay in the compounds. (C) 2002 American Institute of Physics.