Theoretical study of local crystal structure in KZnF3:Fe3+ system

An analysis of the relationship between the EPR trigonal-field parameters and the local crystal structure of KZnF3:Fe3+system is presented by diagonalizing the complete energy matrices for a d5 configuration ion in a trigonal crystal field. We propose a two-layer-ligand model, in which the ligands consist of six nearest-neighbor F− ions in the first layer and eight next nearest-neighbor K+ ions in the second layer. The calculation indicates that the local structure distortion of KZnF3:Fe3+system is due to the displacement of a K+ ion along C3 axis towards the Fe3+ ion, which leads to the shift of the F− ions away from C3 axis. By simulating the EPR low-symmetry parameters D and (a−F), the distorted angles between the Fe3+-F− bonds and C3 axis are determined, Δθ1=2.58°, Δθ2=−1.4° at room temperature (300 K) and Δθ1=2.84°, Δθ2=−1.4° at low temperature (77 K). Those results are in good agreement with the experimental findings Δθ1=2.8±0.3°and Δθ2=−1.1±0.3°.