Effects of composition variation and hydrogenation on magnetocaloric properties of the (Gd1-xTbx)Ni (x=0.1; 0.9) compounds

To identify promising magnetic refrigerant materials, we have studied the influence of composition variations and hydrogenation on the magnetocaloric effect (MCE) of the (Gd1-xTbx)Ni compounds. The end compositions of the series, Gd0.9Tb0.1Ni and Gd0.1Tb0.9Ni crystallize in orthorhombic CrB-type and monoclinic TbNi-type structures, respectively. Hydrogenation boosts the unit cell volume of (Gd,Tb)Ni by more than 20 % upon absorption of 4 at.H/f.u. Hydrogen absorption changes the structure type from TbNi to the CrB-type in Gd0.1Tb0.9Ni. Decrease of the Curie temperature in hydrides reaches similar to 60 K. The magnetocaloric effect in (Gd, Tb)NiHy (y = 0 and 4) obtained by indirect method in the vicinity of T-C revealed similar values of the maximum of specific isothermal entropy change Delta S-T = 20.5 J kg(-1) K-1 for Gd0.9Tb0.1Ni and its hydride Gd0.9Tb0.1NiH4 at mu 0 Delta H = 7 T. We show that the controlled synthesis of hydrides allows us to tailor the magnetocaloric effect in the multicomponent rare earth intermetallics and obtain materials with largely different T-Cs but with the same MCE values that are attractive for use in low-temperature magnetic cooling applications.