Exploring the Curie temperature of the austenitic phase of all-d-metal in reduced dimension

The precise characteristics of the second-order transition, critical behavior, and the austenite phase’s Curie temperature in technologically potential d-d hybridized ferromagnetic shape memory alloy (FSMA), especially in reduced dimensions, remain unknown to the researchers. This article looks into the possible nature of second-order phase transition: critical behavior, exchange interaction decay, and the magnetocaloric response of one such d-d hybridized off-stoichiometric FSMA: Ni ₃₅Mn ₃₅Co ₁₅Ti ₁₅ in ribbon form across its Curie temperature of the austenite phase ( T C A ). A precise value of the critical exponents β ∼ (0.326 ± 0.002), γ ∼ (1.215 ± 0.002), and δ ∼ (4.727 ± 0.038), T C A ≈ (364.48 ± 0.120) K are evaluated using different analytical methods: the modified Arrott plot (MAP), Kouvel-Fisher (KF) plot, and the critical isotherms (CI) analysis. The validity of the critical exponents is confirmed by the Widom-scaling hypothesis: δ = 1 + γ β . The obtained values of the critical exponents indicate that the system does not strictly conform to either the 3D Ising, 3D XY, or 3D Heisenberg models. Instead, it displays characteristics that fall between these three models. The values of critical exponents β and γ demonstrate a greater resemblance to the 3D Ising model, whereas the critical exponents δ and α exhibit a closer proximity to the 3D XY and 3D Heisenberg models. Calculated Rhodes-Wohlfarth Ratio (RWR) ∼ 1.008, indicating the existence of the non-itinerant ferromagnetism or very feeble itinerant ferromagnetism nature of 3d electrons. The decay of the ribbon’s spin-exchange interaction is observed to exhibit a long-range behavior, characterized by the decay law: J(r) ∼ r ^{(– 4.789)}. More significantly, the maximum magnetic entropy change ( Δ S m ) obtained across the Curie temperature is −11.0 J.kg ^-1K ⁻¹ at 20 kOe field, while a working temperature span (Δ T_FWHM) of 7.1 K is found for the same condition. The ribbon’s relative cooling power (RCP) at 20 kOe field is determined to be 445.4 mJ cm ⁻³ (equivalent to 62.3 J.kg ⁻¹), suggesting its potential for miniature engineering design in technological application due to its low constituent cost and its ability to exhibit a substantial refrigerant capacity in a minimal volume.