Hydrogenation, structure and magnetic properties of La(Fe _0.91Si_0.09)₁₃ hydrides and deuterides

Hydrogenation, crystal structure and magnetic properties of La(Fe _0.91Si_0.09)₁₃H(D)_y have been studied by pressure-composition isotherms (PCI), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and magnetization measurements. The maximum absorption capacity is found to be 1.9 H(D) atoms per formula unit as a solid solution. All hydrides and deuterides crystallize in the NaZn₁₃-type cubic structure with the lattice parameter increasing linearly with H(D) concentration. The H(D) absorption enhances the Curie temperature significantly. The magnetic entropy change of the highly H-absorbed compound La(Fe _0.91Si_0.09)₁₃H_1.81 reaches ∼26 J/kg·K under a magnetic field change of 5 T near the Curie temperature T_C = 350 K. No observable isotope effect seems to imply that only the magnetovolume effect is responsible for the strong interplay between magnetism and lattice.