Magnetic entropy change and its temperature variation in compounds La(Fe 1-xCo x) 11.2Si 1.8

Abstract

Magnetic entropy change ΔS of compounds La(Fe 1-xCo x) 11.2Si 1.8 with the cubic NaZn 13-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 ΔS∼13.0 J/kgK under a field of 5 T was achieved in compound LaFe 11.2Si 1.8 at its T C 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, T C 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 T C, which is associated with the strong structural and magnetic interplay in the compounds. © 2002 American Institute of Physics.