The magnetocaloric effect in Ni 50 Mn (37-x) Fe x Sn 13 Heusler alloys

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Abstract
This work investigates the magnetostructural transition and magnetocaloric effect (MCE) in the Ni50Mn(37-x)FexSn13 Heusler alloy series (with x=0, 1, 2, 3, 4 and 5). The polycrystalline ingots were prepared by arc melting and annealed at 850°C for 3 days. Temperature-dependent X-ray diffraction revealed a reversible first-order martensitic transformation from a high-temperature cubic austenite phase to a low-temperature orthorhombic martensite phase. Magnetic and calorimetric measurements showed that the substitution of Mn by Fe systematically shifts the martensitic transition to lower temperatures, leading to its complete suppression for x=5. The alloys exhibit both inverse and conventional MCE, associated with the martensitic and ferromagnetic transitions, respectively. Notably, the sample with x=3 displayed an optimized magnetocaloric performance, achieving a maximum inverse magnetic entropy change (ΔST) of +6.6 J kg−1K−1 and a conventional ΔST of −3.8 J kg−1K−1 under a magnetic field strength change of 50 kOe. Consequently, a large relative cooling power of approximately 491 J kg−1 was obtained for this composition. These results demonstrate that small stoichiometric adjustments in the Fe concentration, combined with precise thermal treatment, allow bulk alloys to achieve refrigerant capacities typically restricted to melt-spun ribbons, establishing the Ni-Mn-Fe-Sn system as a cost-effective and high-performance candidate for solid-state refrigeration.
Funding Information
  • Conselho Nacional de Desenvolvimento Científico e Tecnológico (308100/2022-0)
  • Coordenação de Aperfeiçoamento de Pessoal de Nível Superior