Studies of the EPR parameters and tetragonal distortion for the Cu²⁺ center in aluminium oxide

Abstract

The electronic paramagnetic resonance (EPR) parameters (g factor g_i, and hyperfine structure constants A_i, with i = || and ⊥) and tetragonal distortion of the Cu²⁺ center in Al₂O₃ are unified interpreted from the perturbation formulas for a 3d⁹ ion in tetragonally elongated octahedral. In the calculations, the impurity Cu²⁺ is found to occupy the host trigonally-distorted octahedral Al³⁺ site with the tetragonal elongation distortion due to the Jahn–Teller effect, despite the original trigonal distortion of the host cation site. The contributions to EPR parameters from both the spin–orbit coupling of the central ion and that of the ligands are taken into account. The defect structure of the Cu²⁺ center (characterized by the relative tetragonal elongation ratio η ≈ 4.3% along the C₄ axis) was determined from the calculation. Furthermore, the calculated results agree well with the experimental data and need fewer adjustable parameters than the previous studies.

KEYWORDS:

• Electron paramagnetic resonance (EPR)
• Al₂O₃
• Cu²⁺
• defect structure
• crystal-field theory

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was financially supported by Chinese Natural Science Foundation (grant 11764028), the Open Fund of the Key Laboratory of Nondestructive Testing of Ministry of Education of Nanchang HangKong University (grant number EW2019 08442 and EW201980090).