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

Abstract

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 Tbx(Dy0.5Ho0.5)1-xCo2 (0 ≤ x ≤ 0.5) compounds have transitions of the first order at the Curie temperature (TC) and exhibit a large magnetocaloric effect (with the adiabatic temperature change ΔTad as a measure of the effect) decreasing linearly from ΔTad = 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 TC in Tbx(Dy0.5Ho0.5)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 Tbx(Dy0.5Ho0.5)1-xCo2 in the vicinity of TC. Sets of compounds Tbx(Dy0.5Ho0.5)1-xCo1.75T0.25 (T = Fe, Al) having equal MCE values, appreciable magnetostrictive strains and continuously increased TC are found.