Harnessing room-temperature magnetocaloric effect in hexagonal full-Heusler-like alloy Mn2(Ti0.2Fe0.8)Sn: Paving the way for next-generation applications

Abstract

Room temperature (RT) large cooling power per unit volume, high working temperature span, and moderate magnetocaloric response (MCR) across Curie temperature is achieved in high-quality polycrystalline half-metallic Full Heusler Like Alloy (FHLA): Mn₂(Ti_0.2Fe_0.8)Sn. At RT, this FHLA exhibits an exceptional Mg₃Cd (or Ni₃Sn) type hexagonal structure (Space group P6₃/mmc, no. 194, Strukturbericht designation-D0₁₉) instead of cubic, as confirmed by Raman and X ray diffraction study. A unique, exotic microstructural feature, which is rarely observed in the case of Full Heusler Alloy (FHA), is revealed. DSC (Differential Scanning Calorimetry) and magnetic measurements confirm the Curie temperature to be near the room temperature. The calculated value of the RWR (Rhodes-Wohlfarth Ratio) = 2.759 (>1), signifies that the system exhibits characteristics of an itinerant ferromagnet. For 6 T (Tesla) magnetic field change, across its Curie temperature, this FHLA delivers a working temperature span (ΔT_FWHM) as high as ∼ 20 K, a significant refrigerant capacity (RC) of 285.51 mJ cm⁻³ and; relative cooling power (RCP) of 295.70 mJ cm⁻³, indicating its potency to be utilized in miniaturized engineering design in technology for its low constituent cost, low coercivity, an easy sample synthesis technique, and ability to exhibit substantial cooling power in a minimal volume. Furthermore, this refrigerant could serve as a viable substance for regulating the liquefaction and solidification processes of these harmful VOCs (Common volatile organic compounds) near room temperature. This finding, undoubtedly, enlightens understanding of complex magnetic behaviour and significant MCR effects in FHA, having an unusual exceptional structure, a unique microstructural morphology, and a Curie temperature in the proximity of RT.