Compositional tuning of the magnetocaloric effect in Fe–Nb–B alloys: Critical behavior and phase transition characteristics

Abstract

Magnetic refrigeration, utilizing the magnetocaloric effect (MCE), has emerged as a promising alternative to conventional cooling technologies due to its sustainability and efficiency. In this study, we investigate the influence of Fe composition on the magnetocaloric properties and critical behavior of Fe93-xNb7Bx (x=2, 16, 18, 29) amorphous alloys, focusing on their potential for enhanced performance. The isothermal entropy change (ΔSm) was evaluated under varying magnetic fields, revealing that the x=18 sample exhibits the highest ΔSm value of 1.68J/kg·K at 1.5T. Critical exponents (β, γ, δ, and n), derived using modified Arrott plot (MAP), critical isotherm (CI) and Widom scaling relation (WSR), showing a strong dependence on Fe content. Furthermore, all samples were confirmed to undergo a second-order phase transition, emphasizing the compositional tunability of their magnetic behavior. These findings not only deepen our understanding of the correlation between Fe composition and magnetocaloric performance but also provide a practical framework for optimizing FeNbB alloys. This work paves the way for developing advanced materials tailored for sustainable cooling applications. Keywords: Magnetocaloric effect; Magnetic refrigeration; Second-order phase transition; Critical behavior; Fe–Nb–B alloys