SUPERPOSITION-MODEL ANALYSIS OF THE 2ND-ORDER AND 4TH-ORDER SPIN-HAMILTONIAN PARAMETERS OF FE3+IN THE FLUOROPEROVSKITE COMPOUNDS - NEW EPR STUDY OF FE3+IN KMGF3

A new study of the strong axial EPR spectra of Fe3+ in KMgF3 is presented. In addition to the previously reported spin-Hamiltonian parameters gg and b20 for this axial site, values for the crystal-field parameters b40 and b44 are determined for the first time. Forbidden transitions of the type ΔMs=±2 and ±3, previously unreported, are observed in the EPR spectra. The applicability of the superposition model to the second- and fourth-order spin-Hamiltonian parameters for the strong axial site of Fe3+ in the fluoroperovskite compounds KMgF3, KZnF3, and RbCdF3 is analyzed. It is established that the experimental reported values for the b20 parameter can be fitted if the intrinsic parameter b̄2F of the fluorine ion is -0.09 ± 0.03 cm-1 and the power-law coefficent t2 of b̄2F is taken to be equal to 12 ± 2. On the other hand, it is found that in order to get a consistent model for the FeOF5 cluster center, responsible for the observed strong axial EPR spectra of Fe3+ in the fluoroperovskite compounds, the sign of both spin-Hamiltonian parameters b40 and b44 must be positive and opposite to that of b20. Values for the intrinsic parameter b̄4F of the fluorine ion and for the power-law coefficient t4 of b̄4F are also determined. © 1979 The American Physical Society.