Abstract
Magnetic entropy change ΔS of compounds La(Fe1−xCox)11.2Si1.8 with the cubic NaZn13-type structure was investigated around their Curie temperature TC. It is found that the phase transition is completely reversible, indicating a nature of second order phase transition. The maximum value of |ΔS|∼13.0 J/kg K under a field of 5 T was achieved in compound LaFe11.2Si1.8 at its TC of ∼222 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, TC shifts from 222 to 307 K and entropy change decreases. However, |ΔS| 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 TC, which is associated with the strong structural and magnetic interplay in the compounds.