Investigations of the electron paramagnetic resonance g factors for the trigonal Er3+−VK centers in KMF3 (M=Mg and Zn)

Abstract

The electron paramagnetic resonance g factors gǁ and g⊥ for the trigonal Er3+−VK centers (where VK denotes K+ vacancy) in KMF3 (M=Mg and Zn) are theoretically investigated from the perturbation formulas of the g factors for a 4f11 ion in trigonal symmetry. In these formulas, the contributions to the g factors from the second-order perturbation terms and the admixture of various energy levels are taken into account. In the above trigonal centers, the impurity Er3+ resides in the octahedral M2+ site of both crystals, associated with one VK in the C3-axis due to charge compensation. By analyzing their g factors, we find that the impurity Er3+ in both centers would move towards the VK by an amount ΔZ along the C3-axis due to electrostatic attraction. The calculated g factors for the Er3+ centers based on the above displacements ΔZ show good agreement with the observed values. The validity of the results is discussed.