Glass-forming ability and magnetocaloric performance of Gd18.34+xDy18.33Er18.33-xAl20Fe25 (x = 0, 3, 6, 9) high-entropy amorphous alloys

Abstract

This study employs a low mixing enthalpy–high mixing entropy synergistic design strategy to synthesize Gd_18.34+xDy_18.33Er_18.33-xAl₂₀Fe₂₅ (x = 0, 3, 6, 9) high-entropy metallic glasses (HE-MGs), systematically investigating their glass-forming ability (GFA) and magnetocaloric properties. The results demonstrate that all alloys exhibit distinct ferromagnetic-paramagnetic second-order phase transition (SOPT) near Curie temperatures (T_C) of 75 K, 84 K, 95 K, and 103 K, respectively, validating the predictive significance of the de Gennes factor for T_C tuning in rare-earth-based amorphous systems. Thermodynamic behavior is predominantly governed by f-d hybridization effects induced by 4f electrons, wherein reduced 4f electron concentration weakens hybridization, consequently diminishing thermal stability. Under a 7 T applied field, the maximum isothermal magnetic entropy change (|-ΔS_M^max|) reach 6.59 J kg⁻¹ K⁻¹, 6.57 J kg⁻¹ K⁻¹, 5.06 J kg⁻¹ K⁻¹, and 4.99 J kg⁻¹ K⁻¹; full width at half maximum (ΔT_FWHM) values measure 125.21 K, 138.12 K, 147.87 K, and 150.77 K; and relative cooling power (RCP) attain 825.11 J kg⁻¹, 907.78 J kg⁻¹, 748.30 J kg⁻¹, and 752.54 J kg⁻¹, respectively, highlighting exceptional potential for broad-temperature-range magnetic refrigeration. Scaling theory reveals deviations of critical exponents from mean-field predictions due to microstructural fluctuations and chemical short-range order inherent to the amorphous state. By modulating the Gd/Er ratio, this work simultaneously enhances glass-forming ability (GFA) and magnetocaloric performance, elucidating coupling mechanisms among rare-earth elements, spin-glass effect, and magnetic phase transition. These findings provide experimental and theoretical foundations for developing novel high-efficiency cryogenic magnetic refrigerants.