Tunable magnetic phase transition and magnetocaloric effect in the rare-earth-free Al-Mn-Fe-Co-Cr high-entropy alloys

Abstract

In the present study, the structure, magnetic phase transition, and magnetocaloric performance of Al20Mn20Fe20Co14.5+xCr25.5-x (x = 0, 1, and 2), a series of typical rare-earth-free high-entropy (HE) alloys, were experimentally determined and theoretically analyzed based on first-principle calculation. Ferromagnetic behavior was established and their Curie temperature could be tuned in a wide temperature range, which correlated with Co content; specifically, it increased from 282.8 K for Co14.5Cr25.5 to 345.8 K for Co16.5Cr23.5. In addition, the electronic density of states and magnetic moments associated with each consistent element were analyzed in the HE alloys. Maximum magnetic entropy changes of 1.135, 1.150, and 1.096 J/kgK were obtained for an x of 0, 1, and 2 under a magnetic field change of 5 T. These values are comparable or superior to those of reported 3d metal-based HE alloys. Furthermore, the experimental characterizations and theoretical predications agreed well, which provided an in-depth understanding of the rare-earth-free HE Al-Mn-Co-Fe-Cr alloy system, which is expected to be expanded to other systems in the future.