High magnetic field study of the Dy₂Fe₁₇H_x compounds with x = 0-3.8

The Dy₂Fe₁₇H_x compounds crystallizing in a hexagonal Th₂Ni₁₇-like structure are studied on aligned powder by magnetization measurements carried out in steady (up to 5 T) and pulsed (60 T) magnetic fields at 4.2-300 K. Dy₂Fe₁₇ is a ferrimagnet with T_C = 375 K and a spontaneous moment of 16.5 μ_B/f.u. Magnetization curves recorded for two different crystal orientations for Dy₂Fe₁₇H_x polycrystalline oriented samples show that the insertion of hydrogen in the Dy₂Fe₁₇ crystal lattice significantly modifies the magnetization, Curie temperature and intersublattice exchange interactions of the Dy₂Fe₁₇ phase. The high-field behavior of Dy₂Fe₁₇ is compared with that of its hydrides derivatives. Despite different types of magnetic anisotropy, the high-field behavior of the hydrides and the parent compound is qualitatively similar. Depending upon the composition, they can exhibit easy plane or else conical type anisotropy as for x = 0 and 3, respectively. The low temperature spontaneous magnetization exhibits a moderate composition dependence, it first decreases continuously upon increasing the hydrogen composition up to x = 3 then slightly increases for x = 3.8 reflecting the Fe sublattice evolution. A mean Fe moment of about 2.1 μ_B is derived for Dy₂Fe₁₇H_3.8 composition, this magnetization value is close to that of the original Dy₂Fe₁₇ compound. It is found that the intersublattice coupling between the Fe and Dy sublattices is reduced as illustrated by the decrease of the n_Dy-T coefficient from about 3.3 down to 2.82 T f.u./μ_B for Dy₂Fe₁₇ and Dy₂Fe₁₇H_3.8, respectively.