Correlating critical behaviour and the magnetocaloric effect in Fe–Hf–Zr–B–Cu metallic glasses

Abstract

This research is a systematic experimental investigation of the structural and magnetic properties of a series of Fe_88−xHf_xZr₇B₄Cu₁ (x = 2 & 4) metallic glass ribbons, with a particular emphasis on their magnetocaloric effect (MCE) and magnetic phase transition (MPT) behaviour. Utilizing the Kouvel–Fisher method, critical isotherm analysis, and modified Arrott plots, the critical exponents (β, γ, δ) are estimated to be in close agreement with the 3D-Heisenberg model. Using the Maxwell thermodynamic relation, we determined the maximal isothermal entropy change (−ΔS_M) for the Fe_88−xHf_xZr₇B₄Cu₁ (x = 2 & 4) ribbons. The Fe₈₆Hf₂Zr₇B₄Cu₁ ribbons display an RCP of approximately 61.23 J kg⁻¹ at a Curie transition temperature of 298 K, while the Fe₈₄Hf₄Zr₇B₄Cu₁ ribbons exhibit an RCP of 33.0 J kg⁻¹ at a Curie transition temperature of 312 K under a magnetic field of μ₀H = 2.5 T. This paves the way for the development of innovative magnetic refrigerants that are specific to efficient active cooling technologies near room temperature.