Crystal-field interactions in PrRu2Si2
  Ferromagnetic compound PrRu2Si2 exhibits a giant magnetocrystalline anisotropy of about 400 T. Its ordered moment below Tc=14K reaches 2.7 mB and is parallel to [0 0 1] crystalline direction. We have attributed the magnetism of PrRu2S2 to the Pr ions and performed calculations of the fine electronic structure of the Pr ion in the tetragonal symmetry, relevant to PrRu2Si2 taking into account crystal-field and inter-site, spin-dependent exchange interactions. Spin-dependent interactions have been taken into account by means of molecular-field approximation. The derived energy level scheme is associated with the removal of the degeneracy of the lowest multiplet given by Hund's rules, 3H4. Magnetic and electronic properties resulting from this fine structure are compared with all known experimental results. Our calculations reproduce well the zero-temperature moment, temperature dependence of the magnetic susceptibility, single-crystalline magnetization curves with the anisotropy field of 400T, the specific heat with the sharp peak at Tc as well as inelastic-neutron-scattering data. 
R. Michalski, Z. Ropka, R.J.Radwanski