Defect structure and formation of defect complexes in Cu²⁺-modified metal oxides derived from a spin-Hamiltonian parameter analysis

Abstract

The nearest neighbour oxygen octahedron about copper functional centres in metal oxides has been systematically studied by means of electron paramagnetic resonance (EPR) spectroscopy. In particular, the determined g _∥,zz and spin-Hamiltonian parameters were analysed, finding linear dependences as a function of chemical bonding and local distortion of the oxygen octahedron. Moreover, through the introduction of a dimensionless coordination parameter ξ, different defect structures with respect to the number of coordinated oxygen vacancies may be distinguished. This allows for a distinct assignment of defect complexes between the copper functional centre with one or two oxygen vacancies.

Keywords:

• ferroelectrics
• defect structure
• copper doping
• oxygen vacancy
• defect dipole

Acknowledgments

The continuous support of Professor Stefan Weber (Universität Freiburg) is greatly acknowledged. This research has been financially supported by the DFG through project EI 498/1-1 and the centre of excellence 595 ‘Electrical Fatigue in Functional Materials’.