• L L Li

Articles written in Pramana – Journal of Physics

• Studies of the 𝑔 factors and the superhyperfine parameters for Ni3+ in the fluoroperovskites

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.

• Theoretical studies of the g factors and local structure for Pt3+ in 𝛼-Al2O3

The anisotropic 𝑔 factors and local structure for the trigonal Pt3+ centre in 𝛼-Al2O3 are theoretically investigated from the perturbation formulas of the 𝑔 factors for a $5d^7$ ion in trigonal symmetry. The Pt3+ impurity is found to experience an outward displacement by about 0.18 Å away from the centre of the oxygen octahedron along the $C_3$-axis. The calculated g factors based on the above axial displacement show good agreement with the observed values. Importantly, the pending problem of $+3$ valence state of the doped Pt in 𝛼-Al2O3 is theoretically clariﬁed, and the possibility of Pt+ ($5d^9$) is thus excluded in this work.

• # Pramana – Journal of Physics

Volume 96, 2022
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Posted on July 25, 2019

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