Homogeneity of curie temperature in la (Fe, Si) ₁₃ compounds by Co and C doping

The microstructure and magnetic properties for LaFe _10.85 Co _0.65 Si _1.50.2, LaFe _11.5 Si _1.5C _0.2 and LaFe _10.85 C _0.65Si _1.5 compounds were investigated. The ingots were prepared by 5 kilogram Vacuum Induction Melting Furnace. Then LaFe _10.85Co _0.65Si _1.5 C _0.2 and LaFe _11.5 Si _1.5C _0.2 thin strips were prepared by the strip-casting process. The DSC measurement shows that the maximum latent heat of LaFe _11.5Si _1.5 C _0.2 thin strips has been obtained after annealing at 1353 K for 12 h, longer time annealing seems to be no good for latent heat. Substitute Co for Fe could cause inhomogeneous distribution of Curie temperature &(T-C) in the bulk ingots, but the inhomogeneity can be improved by preparing the strip from the ingot. Under magnetic field changes of 0-1.5 T, the magnetic entropy change near the Curie temperature was about -11.1 J/kg\cK and -}4.0J/kg\cK for LaFe _11.5Si _1.5C _0.2 and LaFe _10.85Co _0.65Si _1.5 C _0.2, respectively.