Spin reorientation and crystal field in the single-crystal hydride HoFe11TiH

We present a study of the hydrogenation effect on structural and magnetic properties of HoFe₁₁Ti single crystal. Single crystal hydride HoFe₁₁TiH_X with H concentration x=1 at. H/f.u. has been prepared. Magnetization measurements along the main symmetry directions of the tetragonal structure have been performed on HoFe₁₁TiH_x (x=0,1) single crystals at applied high magnetic fields up to 80 kOe in the temperature range from 4.2 to 300 K. Torque measurements were carried out in the temperature range 78-700 K in magnetic fields up to 13 kOe. The single-ion magnetic exchange and crystalline-electric-field interaction model has been applied to the fitting of the experimental behavior of the single-crystal HoFe₁₁TiH_x (x=0,1) samples. A set of CEF parameters and mean exchange field has been obtained. Hydrogen atoms have been found to have a significant effect on the second-order crystal field parameter A⁰₂ (A⁰₂=-20.5 Ka^-2₀ for HoFe₁₁Ti and A⁰₂=-118 Ka^-2₀ for HoFe₁₁TiH).