Low-temperature magnetic refrigeration in Gd20Tb20Er20Al20M20 (M = Fe, Co) high-entropy metallic glasses

This paper focuses on the magnetocaloric effect (MCE) of Gd₂₀Tb₂₀Er₂₀Al₂₀M₂₀ (M = Fe, Co) high-entropy metallic glasses (HE-MGs). XRD and TEM results indicate that both HE-MGs are amorphous. Magnetic studies show that both HE-MGs display spin-glass behavior, undergo a second-order phase transition from ferromagnetic to paramagnetic, and exhibit soft magnetic properties at the Curie temperature (T_C). Notable large and broad table-like magnetic entropy change characteristics of Gd₂₀Tb₂₀Er₂₀Al₂₀Fe₂₀ (Gd₂₀Tb₂₀Er₂₀Al₂₀Co₂₀) appear near a T_C of 92 (51) K. Hence, under 7 T magnetic field, |-∆S_M^max|, ∆ T_FWHM, and RCP are 7.83 (10.10) J·kg^-1·K^-1, 120.07 (71.88) K, and 1008.26 (805.70) J·kg^-1, respectively. Furthermore, the modulation of the magnetic and magnetocaloric properties of the samples after substitution of Fe for Co was revealed by the intricate 3d-3d and 3d-4f exchange interactions within the system. The magnetic phase transition critical behaviors in both HE-MGs were analyzed using the scaling law to clarify the deviation of amorphous materials from the mean-field theory. Thus, this study not only highlights the potential of this material for low-temperature magnetic refrigeration applications, but also expands our understanding of its physical properties.