Theoretical study of electron paramagnetic resonance spectrum for Fe3+ ion in KMgF3:Fe3+ system

The electron paramagnetic resonance spectrum of the KMgF3:Fe3+ system has been studied on the basis of the complete energy matrices for the electron-electron repulsion, the ligand-field and the spin-orbit coupling of d5 configuration ion with a trigonal symmetry. A two-layer-ligand model, which includes six F- ions in the first layer and eight next nearest-neighbor K+ ions in the second layer, has been proposed to describe the real ligand-field. By simulating the second-order and fourth-order EPR parameters D and (a-F) simultaneously, a displacement of a K+ ion along C3-axis towards the Fe3+ ion has been found theoretically, and this displacement will give rise to the distortion of the octahedron constructed by six F- ligand ions in the first layer. ΔZ is used to describe the displacement of a K+ ion along C3-axis towards the Fe3+ ion, and two angles θ1 and θ2 between the Fe3+-F- band and C3-axis are taken to describe the local distortion along the [1 1 1] direction. By adjusting the ΔZ, the range of the local distortion parameters Δθ1=5.54∘-6.07∘, Δθ2=-4.60∘ to -5.00∘ are determined, and the EPR spectrum of the KMgF3:Fe3+ system has been satisfactorily explained by the two-layer-ligand model.