Structural and high-field magnetic properties of Laves phase RFe2-H hydrides.

The crystal structure and magnetic properties of the multicomponent compounds (Tb_1−xY_x)_0.8Sm_0.2Fe₂H_z (x = 0, 0.2, 0.4, 0.6, 0.8, 1; z = 0 and 3.7) are investigated. The compounds crystallize in the MgCu₂ type of structure. While the parent compounds Tb_0.8Sm_0.2Fe₂ and Y_0.8Sm_0.2Fe₂ are single phase, we detect 5%–8% of a second phase with a crystal structure of the PuNi₃ type (space group R3m) in the alloys with 0.2 ≤ x < 0.8. Hydrogen absorption does not change the space group of the (Tb,Y,Sm)Fe₂ compounds but boosts significantly the lattice parameter a. A large volume change of ΔV/V ∼ 28% upon hydrogen absorption is observed. By applying high magnetic fields up to 58 T, we observed rotations of the magnetic sublattices and hence we were able to determine the critical transition fields, H, from the ferrimagnetic to the ferromagnetic state and the inter-sublattice exchange parameter λ. The magnetic compensation occurs at x ≈ 0.6 and 0.2 in (Tb_1−xY_x)_0.8Sm_0.2Fe₂H_z at z = 0 and 3.7, respectively. While maintaining the collinear magnetic structure, the phenomenon of compensation in hydrides should be observed at x ≈ 0.4. [ABSTRACT FROM AUTHOR]