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Electron paramagnetic resonance; crystal- and ligand-field theory; hyperfine interactions; Ni³⁺; KMgF³; RbCaF³; CsCaF³.

The 𝑔 factors and the ligand superhyperfine parameters $A'$ and $B'$ for Ni³⁺ in KMgF₃, CsCaF₃ and RbCaF₃ are theoretically studied from the formulas of these parameters for a 3d⁷ ion under octahedral environments in the weak field scheme. The unpaired spin densities for the fluorine 2s, 2p$_{\sigma}$ and 2p$_{\pi}$ orbitals are quantitatively determined from the molecular orbital and configuration interaction coefficients based on the cluster approach. The calculated results show good agreement with the experimental data, based on only one adjustable parameter (i.e., the proportionality factor 𝜌 related to the ligand s- and p-orbitals). The superhyperfine parameters for the axial and planar ligands in RbCaF₃:Ni³⁺ are satisfactorily interpreted from the different impurity–ligand distances due to the elongation of the ligand octahedron during cubic-to-tetragonal phase transition.

Y X Hu¹ S Y Wu^{1 2} X F Wang¹ L L Li¹

1. Department of Applied Physics, University of Electronic Science & Technology of China, Chengdu 610054, People's Republic of China
2. International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016, People's Republic of China

Published

June 2009

Manuscript received

23 October 2008

Manuscript revised

12 April 2009

Accepted

1 May 2009