Giant low-field magnetocaloric effect in ferromagnetically ordered Er 1-x Tm x Al 2 (0 < x < 1) compounds

Magnetocaloric material is the key working substance for magnetic refrigerant technology, for which the low-field and low-temperature magnetocaloric effect (MCE) performance is of great importance for prac-tical applications at low temperatures. Here, a giant low-field magnetocaloric effect in ferromagnetically ordered Er1-xTmxAl2 (0 < x < 1) compounds was reported, and the magnetic structure was characterized based on low-temperature neutron powder diffraction. With increasing Tm content from 0 to 1, the Curie temperature of Er1-xTmxAl2 (0 < x < 1) compounds decreases from 16.0 K to 3.6 K. For Er0.7Tm0.3Al2 compound, it showed the largest low-field magnetic entropy change (-ASM) with the peak value of 17.2 and 25.7 J/(kg K) for 0-1 T and 0-2 T, respectively. The (-ASM)max up to 17.2 J/(kg K) of Er0.7Tm0.3Al2 compound for 0-1 T is the largest among the intermetallic magnetocaloric materials ever reported at temperatures below 20 K. The peak value of adiabatic temperature change (ATad)max was determined as 4.13 K and 6.87 K for 0-1 T and 0-2 T, respectively. The characteristic of second-order magnetic tran-sitions was confirmed on basis of Arrott plots, the quantitative criterion of exponent n, rescaled univer-sal curves, and the mean-field theory criterion. The outstanding low-field MCE performance with low working temperatures indicates that Er1-xTmxAl2 (0 < x < 1) compounds are promising candidates for magnetic cooling materials at liquid hydrogen and liquid helium temperatures.(c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.