Relating microstructure to magnetocaloric properties in RE36Tb20Co20Al24 (RE = Gd, Dy or Ho) high-entropy metallic-glass microwires designed by binary eutectic clusters method

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.