Magnetic refrigeration properties of Gd20Tb20Er20Cu20M20 (M=Fe, Co) high-entropy metallic glasses with refrigeration temperature span of exceeding 130 K

In this paper, Gd20Tb20Er20Cu20M20 (M = Fe, Co) high entropy metallic glasses (HE-MGs) are designed, and their microstructure, magnetic behavior, magnetocaloric effect (MCE) and critical behavior are studied in detail. All prepared alloy ribbons exhibit the feature of disordered structure. Two samples exhibit distinct spin glass behavior at 62 K and 37 K, respectively. Two HE-MGs undergo the second-order phase transition (SOPT) from ferromagnetic state to paramagnetic state at 113 K and 77 K, which are near liquid hydrogen temperature. The remarkable MCEs are achieved by two HE-MGs through the combination of SOPT and spin glass behavior. Under the applied magnetic field of 0-7 T, the peak isothermal magnetic entropy change (|-Delta SMmax|) and RCP are 6.7 J & sdot;kg- 1 K- 1 and 900.9 J & sdot; kg- 1 (for M = Fe), 8.5 J & sdot; kg- 1 K- 1 and 763.7 J & sdot; kg- 1 (for M = Co). Due to spin behavior and complicated compositions, the phase transition temperature span (Delta TFWHM) of the Gd20Tb20Er20- Cu20M20 is exceeding 130 K under 0-7 T. The microstructure fluctuations and chemical short-range order cause respective phase transition deviate from mean field model. The Gd20Tb20Er20Cu20M20 (M = Fe, Co) HE-MGs show excellent MCE properties and can be manufactured easily, making them promising for cryogenic temperature magnetic refrigerant applications.