Large magnetocaloric effect of Tm1 − xYxGa (0 ≤ x ≤0.8) compounds with second-order magnetic transition around liquid helium temperature

Abstract

A systematic investigation about Tm substitution by rare earth Y atoms in Tm1 − xYxGa (0 ≤ x ≤0.8) compounds on the magnetic properties and magnetocaloric effect (MCE) is presented. Among Tm1 − xYxGa compounds, Tm0.4Y0.6Ga exhibits the optimized working temperatures around the boiling point of liquid helium and large MCE. It undergoes a ferromagnetic (FM) to antiferromagnetic (AFM) transition at TFA = 2.8 K and an AFM to paramagnetic transition at TN = 5.4 K with increasing temperature, respectively. Moreover, the characteristic of second-order magnetic transition was confirmed on the basis of Arrott plots, rescaled universal curves, mean-field theory criterion, and the quantitative criterion of exponent n. Large MCE with the maximum magnetic entropy change of 6.4, 10.1, and 15.6 J/kg K and the maximum adiabatic temperature change of 2.4, 4.2, and 8.4 K for the field changes of 0–1, 0–2, and 0–5 T was observed, respectively. Consequently, the properties of low working temperatures, the characteristic of second-order magnetic transition, and good performance of MCE indicate that Tm0.4Y0.6Ga compounds could be a promising candidate of magnetocaloric materials in the application of helium liquefaction.