Effect of Hydrogenation on the Magnetic and Magnetocaloric Properties of Rare Earth Intermetallic Compounds Tb0.33Ho0.33Er0.33Ni and Dy0.33Ho0.33Er0.33Ni

Multicomponent rare earth intermetallic compounds Tb0.33Ho0.33Er0.33Ni and Dy0.33Ho0.33Er0.33Ni crystallize in orthorhombic FeB-type structure (Space group Pnma, No. 62, oP8) and order ferromagnetically at 59 K and 40 K (T-C) respectively. Hydrides of these samples show a presence of similar to 10-nm size nanoparticles with unit cell volume expansion. Magnetization measurements reveal that hydrides Tb0.33Ho0.33Er0.33NiH1.9 and Dy0.33Ho0.33Er0.33NiH1.9 remain paramagnetic from 300 K down to 5 K. Magnetization value at 5 K in 70 kOe field is similar to 5.1 mu(B)/f.u. and 5.5 mu(B)/f.u., respectively, for Tb0.33Ho0.33Er0.33NiH1.9 and Dy0.33Ho0.33Er0.33NiH1.9 samples. Despite the lack of ferromagnetic order, hydrides exhibit large low-temperature magnetocaloric effect with maximum isothermal magnetic entropy change values of about - 11.6 Jkg(-1) K-1 at 14 K and - 12.9 Jkg(-1) K-1 at 8 K respectively for 50 kOe magnetic field change.