Anisotropic magnetic properties of single crystals ofSmRh4B4

The magnetic susceptibility of single crystals of ${\mathrm{SmRh}}_4$ ${\mathrm{B}}_4$ has been measured for two orientations of the crystals with respect to the applied field H. At low temperatures, the easy direction of magnetization is perpendicular to the tetragonal c axis, while for temperatures higher than 73 K, the easy axis of magnetization is parallel to the c axis. The data have been analyzed by including intermediate coupling of the lowest three J manifolds of the ${\mathrm{Sm}}^{3+}$ ion, crystal-field interactions, and conduction-electron polarization effects. The anisotropy crossover is shown to result primarily from a competition between the anisotropy of the crystal-field energy levels in the ground (J=(5/2) manifold and the anisotropy of Van Vleck terms due to mixing of the J=(5/2 and J= 7) / 2 manifolds.