Magnetocaloric effect in a cluster-glass system Ho5Pd2-xNix

In order to investigate the effect of chemical pressure on the large magnetocaloric effect in Ho5Pd2, we conducted X-ray diffraction, magnetization, and specific heat measurements on Ho5Pd2-xNix(0 <= x <= 1.0) rare-earth intermetallic compounds. The linear x dependence of the lattice constant a suggests that Ni is replaced with Pd in the case of Ho5Pd2-xNix (0 <= x <= 0.5). The spin-glass transition temperature T-g and paramagnetic Curie temperature theta(p) indicate a weak oscillatory x dependence. However, the magnetic entropy change -Delta S-m and the relative cooling power (RCP) are rapidly suppressed with increasing x. These large reductions in -Delta S-m and RCP cannot be explained only in terms of normal Ruderman-Kittel-Kasuya-Yoshida (RKKY)-type indirect exchange interactions.