The influence of the crystal structure on the magnetic ordering in RT2X2 and RTX3 compounds

In this paper, the correlation between the crystal structure and magnetic ordering in ternary RT2X2 and RTX3 (R is the rare earth metal, T the 3d, 4d or 5d transition metal and X = Si or Ge) compounds is presented. These compounds crystallize in three types of crystal structure which have been derived from the tetragonal BaAl4 structure: ThCr2Si2, CaBe2Ge2 and BaNiSn3. The position of R atoms in these crystal structures causes the anisotropic character of magnetic interaction between the R ions, and the Ising-like model can be used to explain the stability of magnetic ordering schemes discovered by neutron diffraction experiments in many intermetallic compounds. The analysis of the magnetic structure of RT2X2 (X = Si, Ge) compounds reveals a strong dependence of magnetic ordering on the a/c ratio. The data are briefly discussed in terms of the RKKY theory and crystalline–electric field model.