Magnetic entropy change and microstructure of LaFe11.6-Ni Si1.4 alloys enhanced by Ni doping and annealing treatment

Magnetic properties and magnetocaloric effect of LaFe _{11.6- x}Ni _xSi _1.4 alloys upon Ni substitution have been systematically investigated. It was found that the substitution of Fe by Ni elements results in an increase in the Curie temperature T _C, and affects the LaFe _{11.6- x}Ni _xSi _1.4 ( x = 0, 0.1, 0.2) alloys magnetocaloric properties. A maximum shift in the Curie temperature T _C of about 8.97 K compared with the base compound ( x = 0). Through equilibrium organization analysis, the partial substitution of Ni for Fe in LaFe _{11.6- x}Ni _xSi _1.4 alloys promotes the formation of 1:13 phase and the elimination of impurity phases significantly. About heat treatment, the magnetic entropy change (−Δ S _M) of LaFe _{11.6- x}Ni _xSi _1.4 ( x = 0.2) alloy annealed at 1343 K is 16.01 J/(kg⋅K) under a 2.5 T magnetic field. This indicates that optimizing the annealing temperature can beneficially accelerate the eutectic reaction process and result in an increase in the 1:13 phase content, thereby enhancing its magnetocaloric properties. Therefore, the microstructure and magnetocaloric properties of LaFe _{11.6- x}Ni _xSi _1.4 alloys could be effectively modulated by optimizing the annealing process, which provides a significant technical reference for the practical application near-room temperature magnetic refrigeration technology.