Abstract: The new high-entropy metallic-glasses (HE-MGs) are designed by using Dy and Ho to replace Gd in Gd₃₆Tb₂₀Co₂₀Al₂₄ alloy based on the binary eutectic clusters method. Compared with the equiatomic Gd₂₅Tb₂₅Co₂₅Al₂₅ HE-MG, the non-equiatomic RE₃₆Tb₂₀Co₂₀Al₂₄ (RE = Gd, Dy, or Ho) alloys show better glass-forming ability, which is attributed to the deep binary eutectic compositions used for alloy design. All RE₃₆Tb₂₀Co₂₀Al₂₄ alloys undergo second-order magnetic transition. An extreme peak value of magnetic entropy change is obtained as 10.3 J kg^-1 K^-1 (5 T) for the Ho₃₆Tb₂₀Co₂₀Al₂₄ alloy. In-situ high-energy synchrotron X-ray diffraction was conducted to observe the microstructural difference among non-equiatomic samples at cryogenic temperatures. The results indicate that Gd₃₆Tb₂₀Co₂₀Al₂₄ alloy possesses a relatively large average value of the dispersion of local clusters at a low-temperature range. This, combined with the critical exponent β close to 0.5 of Gd₃₆Tb₂₀Co₂₀Al₂₄ alloy, leads to its widest working temperature span among non-equiatomic samples. This work successfully establishes the connection between microstructure and magnetocaloric properties of HE-MGs, which is beneficial for understanding the physical mechanism of the magnetocaloric behaviors of HE-MGs.

Key words: High-entropy metallic-glass, Magnetocaloric effect, High energy synchrotron X-ray diffraction, Cryogenic temperature