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

• Published in: Journal of solid state chemistry Vol. 296; p. 121980
• Main Authors: Georgopoulou-Kotsaki, E., Giannouri, M., Syskakis, E.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-04-2021
• Subjects: ac-Magnetic susceptibility; Electrical resistivity; Magnetic ordering; Magneto-caloric effect; Solid state reaction; Transition metal compounds; ac-Magnetic susceptibility; Magneto-caloric effect; Transition metal compounds; Electrical resistivity; Magnetic ordering; Solid state reaction
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2021.121980

Polycrystalline powders of Mn5-xFexSi3 (x ​= ​2.5, 3.0, 3.5, 4.0) compounds (Mn5Si3-type, space group P63/mcm, No. 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 χac 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 ​> ​300 ​K. At T ​< ​300 ​K, ρ(T) shows a linear temperature dependence with a change of slope observed upon approaching the corresponding magnetic ordering temperature. For the samples sintered under flowing Ar-4%H2 atmosphere, the electrical properties are similar to those of the samples sintered under HV, while a strong enhancement of χac was observed.
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•Polycrystalline Mn5-xFexSi3 (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 18–915 ​K is metallic for all x and almost temperature independent at T ​≥ ​300 ​K.•The samples sintered under Ar-4%H2 showed a strong enhancement of ac-magnetic susceptibility and improved densification.