Theoretical study of local structure of tetragonal Fe3+ center in layered perovskite Rb2ZnF4 and Rb2CdF4

The electron paramagnetic resonance spectra of layered perovskite Rb2ZnF4 and Rb2CdF4 doped with Fe3+ are studied by means of a 252 x 252 complete energy matrix for a 3d5 configuration ion in a tetragonal ligand-field. The local structure parameters Rperpendicular and Rparallel for Rb2ZnF4:Fe3+ and Rb2CdF4:Fe3+ systems are determined. The calculations show that the local lattice of the Rb2ZnF4:Fe3+ and Rb2CdF4:Fe3+ systems display a compression distortion relative to the regular octahedron. Besides, the value of Rperpendicular in Rb2ZnF4 and Rb2CdF4 crystals is, respectively, larger than that in Rb2ZnF4:Fe3+ and Rb2CdF4:Fe3+ systems. This may be ascribed to the fact that Fe3+ ions have the smaller ionic radius and larger charge in comparison to Zn2+ and Cd2+ ions. In the end, the relative curves of 104b20 vs. ΔR (ΔR Rperpendicular - Rparallel ) for these two systems are plotted which satisfy an approximately linear relation