Effect of hydrogenation on spin-reorientation phase transitions and magnetic anisotropy constants of RFe11Ti single crystals (R=Lu, Ho, and Er)

The magnetic anisotropy and spin-reorientation phase transitions in single crystals of the RFe₁₁Ti (R=Lu, Ho, and Er) compounds and their hydrides are investigated. Measurements are carried out on capacitance and torque magnetometers. The magnetic anisotropy constants K ₁ and K ₂ are determined by the mathematical processing of experimental magnetization curves in terms of the phenomenological theory of the anisotropic ferromagnet magnetization. It is demonstrated that the hydrogenation strongly affects the magnitude and the sign of magnetic anisotropy constants, as well as the spin-reorientation phase transitions. The hydrogenation of the HoFe₁₁Ti compound leads to the change in sign of the magnetic anisotropy constant K ₁. The inference is made that a change in the atomic volume and the axial ratio c/a cannot result in the observed effects. A change in the magnetic anisotropy constants upon hydrogenation is primarily due to the change in the interaction of the quadrupole moment of a 4f electron subshell of rare-earth ions with surrounding ions of the crystal lattice and also with valence and conduction electrons.