Synthesis of magnetocaloric Mn5-xFexSi3 (2.5≤x≤4.0) compounds and the influence of various sintering atmospheres on the magnetic and electrical properties

Highlights: • Polycrystalline Mn_5-xFe_xSi₃ (x=2.5, 3.0, 3.5, 4.0) compounds synthesized by solid state reaction method. • Samples were sintered under High Vacuum (HV) conditions as well as under Ar-4%H₂ conditions. • The electrical resistivity in the range 18–915K is metallic for all x and almost temperature independent at T≥300K. • The samples sintered under Ar-4%H₂ showed a strong enhancement of ac-magnetic susceptibility and improved densification. Polycrystalline powders of Mn_5-xFe_xSi₃ (x=2.5, 3.0, 3.5, 4.0) compounds (Mn₅Si₃-type, space group P6₃/mcm, N_o. 193) were prepared by solid state reaction of pure Mn, Fe and Si powders under High Vacuum (HV) conditions at T=1000°C. Samples were sintered at T=1100°C under HV as well as under Ar-4%H₂ conditions. X-ray Diffraction (XRD) analysis revealed that the compounds crystallize with hexagonal symmetry in accordance with previous reports. The χ_ac susceptibility measurements for the samples sintered under HV conditions show systematic strengthening of the ferromagnetic (FM) state upon increasing x. The electrical resistivity, ρ, remains metallic for all x, with a very weak temperature dependence at T>300K. At T2 atmosphere, the electrical properties are similar to those of the samples sintered under HV, while a strong enhancement of χ_ac was observed.