Studies of EPR spectra and defect structure for Er3+ ions in BaF2 and SrF2 crystals

The local lattice structure and electron paramagnetic resonance (EPR) spectra have been studied systematically by diagonalizing 364 × 364 complete energy matrices for a f11 ion in a trigonal ligand-field. By simulating the calculated Stark levels and EPR parameters to the experimental results, the shift parameters are determined for Er3+ ions in BaF2 and SrF2. The results show that the trigonal center is attributed to an interstitial F− ion located at the [1 1 1] axis of the cube, and the nearest ligand close to the charge compensator has a displacement towards central ion by 0.042 Å for L center in BaF2:Er3+ and 0.026 Å for J center in SrF2:Er3+, respectively. Moreover, the relationships between g-factors and shift parameter ΔZ as well as orbit reduction factor k′ are discussed.

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► We construct 364 × 364 complete energy matrices for f11 configuration ion.
► The optical and EPR spectra of Er3+ in BaF2 and SrF2 have been investigated.
► The defect structures for BaF2:Er3+ and SrF2:Er3+ systems have been determined.
► The new set of crystal-field parameters for BaF2:Er3+ have been derived.
► The relationship between g-factors and shift parameter ΔZ has been discussed.