Synthesis, structure and magnetic properties of Sm_1.2Ho_0.8Fe₁₇Н_x (x = 0; 4.4)

Intermetallic compounds based on rare-earth metals and iron are by far the most promising materials for permanent magnets. In this work, the multicomponent compound Sm_1.2Ho_0.8Fe₁₇ was prepared by induction melting. The hydride Sm_1.2Ho_0.8Fe₁₇H_4.4 with a high hydrogen content was obtained by direct hydrogenation of the intermetallic compound. The rhombohedral Th₂Zn₁₇-type of structure (space group R3m) is inherent to parent compound and hydride as well. The effect of hydrogenation on the magnetic properties of Sm_1.2Ho_0.8Fe₁₇ was investigated. Curie temperature of the hydride Sm_1.2Ho_0.8Fe₁₇H_4.4 is higher than that of parent compound by ΔT_C = 138 K. The hydrogen embedded in Sm_1.2Но_0.8Fe₁₇ crystal lattice increases the saturation magnetization (σ_S) at T = 300 K, but does not significantly affect σS at Т = 4.2 K. The ferrimagnetic structure is retained in magnetic fields up to 58 T in the parent compound, while, in the hydride, there is a spin-reorientation phase transition observed at 55 T. It is found that the parameter of the intersublattice exchange interaction decreases significantly in the hydride Sm_1.2Ho_0.8-Fe₁₇H_4.4 (and in the nitride Sm_1.2Ho_0.8Fe₁₇N_2.4) which is associated with boosting of the unit-cell volume and distances between magnetic ions.