• Feng Wen-Lin

Articles written in Pramana – Journal of Physics

• Studies of the defect structure from the calculations of optical and electron paramagnetic resonance spectra for Ni2+ centre in $\alpha-LiIO_{3}$ crystal

By calculating the optical spectrum band positions and EPR parameters (𝑔 factors, $g_{\parallel}$ , $g_{\perp}$ and zero-field splitting 𝐷) by diagonalizing the complete energy matrix of 3d8 ions in trigonal symmetry, the defect structure of Ni2+ centre in 𝛼-LiIO3 crystal is studied. It is found that to reach the good fits of optical and EPR data between calculation and experiment, the Ni2+ ion should shift by $\Delta z \approx 0.298$ Å along C3 -axis and the O2− ions between the Ni2+ ion and Li+ vacancy (V$_{Li}$) should be displaced away from the V$_{Li}$ by $\Delta x \approx 0.097$ Å because of the electrostatic interaction. The results are discussed.

• Electron paramagnetic resonance parameters of Mn4+ ion in h-BaTiO3 crystal from a two-mechanism model

The EPR parameters (𝑔 factors $g\parallel$, $g\perp$ and zero-field splitting 𝐷) of Mn4+ ion in h-BaTiO3 crystal are calculated from the complete high-order perturbation formulas based on a two-mechanism model for the EPR parameters of $3d^{3}$ ions in trigonal symmetry. In the model, not only the widely used crystal-field mechanism, but also the charge-transfer mechanism (which is not considered in crystal-field theory) are included. The calculated results are in reasonable agreement with the experimental values. The relative importance of charge-transfer mechanism to EPR parameters and the defect structure of Mn4+ centre in h-BaTiO3 crystal obtained from the calculations are discussed.

• # Pramana – Journal of Physics

Volume 94, 2020
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Posted on July 25, 2019

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