Engineering Light-Element Modified LaFe_11.6Si_1.4 Compounds Enables Tunable Giant Magnetocaloric Effect

Magnetocaloric refrigeration is one of the most promising next-generation solid-state caloric techniques to revolutionize the traditional air-compression technique. The La(Fe,Si)₁₃-based materials are recognized as candidates with potential for practical applications. However, flexible strategies to improve the Curie temperature (T_C) and further achieve the tunable giant magnetocaloric effect (GMCE) still need to be developed. Here, the systematic experimental investigation on a series of light elements (C, F, S) modified LaFe_11.6Si_1.4 compounds are presented. It is found that all modified samples exhibit a higher T_C, with a negligible impact on the thermal hysteresis. The GMCE performance in C- and S-modified samples is significantly degraded, but the maximum magnetic entropy change |Δ s_m| for the optimally doped F sample can be well maintained at 19.2 J kg⁻¹ K⁻¹ for a field change of 2 T. The preferential site occupancy of dopants is determined, and the microstructural observation and metastable atomic changes have also been analyzed. It is concluded that interstitial doping is more efficient to shift T_C. The first-order transition can however not be maintained upon doping due to changes in the hybridization. These findings highlight the importance of the interplay between the lattice pressure effect and the covalent hybridization for this material family.