Large magnetocaloric entropy change in ferrimagnetic Er_1-xCo₂ systems at cryogenic temperatures: the role of erbium deficiency

Abstract

We discussed the binary rare-earth-based intermetallic Er_1-xCo₂ systems structurally, magnetically and in the field of the magnetic cooling with the effect of Er deficiency on all these properties. Four series of Er_1–xCo₂ (x = 0.00; 0.04, 0.06, 0.08 and 0.15) samples were prepared via arc-melting method and investigated as magnetic refrigerants. A high magnetocaloric effect was detected in these systems that follow a first-order magnetic transition. Magnetic entropy changes were most important compared to those of other Laves phase compounds. Structures of x = 0.00–0.06 compounds were indexed as a cubic state of space group Fd-3m with MgCu₂ structure-type, e.g. as Laves phase. Whereas compounds of x = 0.08 and x = 0.15, due to the presence of some peaks, were attributed to rhombohedral as a second phase symmetry of space group R-3m with PuNi₃ structure type. All systems were characterized by ferrimagnetic to paramagnetic transition upon temperature increase. Er_1–xCo₂ compounds exhibited significant relative cooling power values, i.e. at x = 0.06 sample, achieving approximately 585.52 J/kg at 7 T, making them appropriate candidates for the magnetic refrigeration technique.