EPR Study of Cu 2+ Impurity Centre in WO 3

Zeitschrift Für Naturforschung A

2005

The gyromagnetic factors g , g ⊥ and the hyperfine structure constants A and A ⊥ of the tetragonal Cu 2+ center in KTaO 3 are theoretically studied in this work. Based on the analyses of the electron paramagnetic resonance results of this center, it is found that the impurity Cu 2+ occupies the octahedral Ta 5+ site, associated with a nearest-neighbouring oxygen vacancy V O along the C 4 axis. Due to the electrostatic repulsion of V O , Cu 2+ is displaced away from V O by ∆ Z(≈ −0.29Å) along the C 4 axis. The theoretical values of the g and A factors based on the above defect structure and the impurity displacement agreee reasonably with the experimental data.

Section: Discussionsupporting

confidence: 84%

“…Based on the theoretical calculations in this work and various observed results for Cu 2+ in some elongated oxygen octahedra [18,20,21], we suggest that these signs may be negative.…”

Section: Calculationssupporting

confidence: 65%

Theoretical Studies on the Gyromagnetic Factors and the Hyperfine Structure Constants for the Tetragonal Copper Center in KTaO₃

Zeitschrift Für Naturforschung A

2005

“…In fact, expansion of the planar impurity-ligand distances leads to a slight decrease in the difference between the bonding lengths parallel with and perpendicular to the four-fold axis, and hence in tetragonal dis-tortion, yielding a larger (or better) value of the calculated g ⊥ . Although the sign of the experimental A was not determined in [8], theoretical studies in this work support the negative sign of A , as did some similar EPR investigations on Cu 2+ in elongated oxygen octahedra [22,23].…”

Section: Discussionsupporting

confidence: 74%

Investigations of the Defect Structure for Cu²⁺ in SrLaAlO₄

Wei

Zeitschrift Für Naturforschung A

2005

The defect structure for Cu 2+ in SrLaAlO 4 is theoretically investigated by the perturbation formulas of the spin Hamiltonian parameters (g factors g , g ⊥ and the hyperfine structure constants A and A ⊥ ) for a 3d 9 ion in tetragonally elongated octahedra. Based on these studies, the tetragonal center may be attributed to Cu 2+ occupying the host Al 3+ site, associated with one hole delocalized at the four oxygen ligands in planar coordination. Furthermore, the four Cu,O bonds (perpendicular to the four-fold axis) are found to suffer an outward stretch of about 0.06Å due to (i) the local tenseness in this plane, arising from the size mismatching substitution of the smaller Al 3+ by the larger Cu 2+ and (ii) the weaker electrostatic attraction of the less charged Cu 2+ acting upon the four oxygen ions containing the delocalized hole. The calculated spin Hamiltonian parameters agree well with the experimental data. The defect structure of this center is discussed.

“…) is also observed for the orthorhombic (CuO 6 ) 10− cluster in WO 3 [19]. Therefore, the sign of the A z should be negative.…”

Section: Discussionmentioning

confidence: 70%

Theoretical explanation of EPR parameters for Cu²⁺ ion in TiO₂ crystal

Physica Status Solidi (b)

2004