Effect of partial Gd substitution on the magnetic and magnetocaloric properties in Dy-Ho-Gd-Co multicomponent compounds

Abstract

The magnetic and magnetocaloric properties of polycrystalline (Dy0.9Ho0.1)1−xGdxCo2 (0.0 ≤ x ≤ 0.15) solid solutions were investigated experimentally using magnetic measurements; the Landau theory was also applied to clarify peculiarities of the magnetic phase transition in the compounds. X-ray diffraction patterns taken at room temperature exhibit the existence of the C15 cubic Laves phase structure for all samples under study. The lattice parameter increased from 0.7186 for x = 0.0 to 0.7194 nm for x = 0.15 and the Curie temperature TC increases from 130 to 183 K as the Gd content increases to x = 0.15. The isothermal entropy change ΔSmag was calculated according to magnetic measurements using the thermodynamic Maxwell's relation. A decrease in entropy change with the increase of Gd content has been observed. Under an external field change of from 0 to 3 T, the maximum entropy change decreased from 8.1 for x = 0.0 to 4.3 J kg−1 K−1 for x = 0.15. The effect of increasing the Gd amount in the (Dy0.9Ho0.1)1−xGdxCo2 solid solutions on their magnetic and magnetocaloric properties is discussed.