Persistent values of magnetocaloric effect in the multicomponent Laves phase compounds with varied composition

In this work we investigate the magnetocaloric effect (MCE) in the multicomponent RCo₂-type compounds with a Laves phase structure varied by substitutions within both the rare earth (R) and Co sublattices. Complex substitutions increase dramatically the Curie temperatures at which the maximum MCE is observed. The Tb_x(Dy_0.5Ho_0.5)_1-xCo₂ (0 ≤ x ≤ 0.5) compounds have transitions of the first order at the Curie temperature (T_C) and exhibit a large magnetocaloric effect (with the adiabatic temperature change ΔT_ad as a measure of the effect) decreasing linearly from ΔT_ad = 3.6 K to 2.2 K (at μ₀ΔH = 1.8 T) as x varies between 0 and 0.5. At the increasing Tb concentrations x above 0.5, the transition at T_C in Tb_x(Dy_0.5Ho_0.5)_1-xCo₂ changes order from first to the second while MCE remains constant ∼2.2 K. Volume magnetostriction is of the order of 1000 ppm in Tb_x(Dy_0.5Ho_0.5)_1-xCo₂ in the vicinity of T_C. Sets of compounds Tb_x(Dy_0.5Ho_0.5)_1-xCo_1.75T_0.25 (T = Fe, Al) having equal MCE values, appreciable magnetostrictive strains and continuously increased T_C are found.