Exchange interactions and magnetocrystalline anisotropy of rare earth - cobalt compounds with CaCu5-type structure

The magnetic moments, easy directions and hard axis magnetization behaviour in high magnetic fields have been studied in detail on single crystals of the quasibinary compounds Y1-xNdxCo5, Y1-xGdxCo5and TbxY1-xCo5+0.1xat temperatures of 4.2 - 400 K. The easy directions of Gd-compounds remain parallel to their c-axes throughout the whole temperature range. The spin reorientations from c-axis to c-plane take place during cooling of Nd- and Tb-compounds at temperatures which are the higher, the larger is x. The hard direction magnetization curves at 4.2 K were used for calculating the first and second anisotropy constants of the rare earth magnetic sublattices as well as molecular fields acting on rare earth ions from the cobalt sublattice. It is shown that magnetocrystalline anisotropies of Nd- and Tb-sublattices are well described in terms of the single-ion model while Gd-sublattice has negligible anisotropy energy. The influence of magnetocrystalline anisotropy on spontaneous magnetic moments of both sublattices at 4.2 K is shown for Y1-xTbxCo5+0.1xcompounds.