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 a re investigated. Measurements are carried out on capacitance and torque mag netometers. 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-reorient ation phase transitions. The hydrogenation of the HoFe11Ti compound leads t o 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 constan ts 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 sur rounding ions of the crystal lattice and also with valence and conduction e lectrons. (C) 2001 MAIK "Nauka/Interperiodica".