Photo‐EPR and magneto‐optical spectroscopy of iron centres in ZnO

Abstract

AbstractZnO has attracted increasing interest as promising material for optoelectronics and spintronics. Magnetic properties of ZnO can be controlled by doping with transition metal ions among which Fe3+ is one of the interesting candidates. We report on the properties of Fe3+ centres in hydrothermally and chemical vapour transport grown ZnO single crystals investigated by photo‐electron paramagnetic resonance (EPR) and optical spectroscopy. Detailed magneto‐optical studies of Zeeman components of spin‐forbidden electric dipole transitions 4T1(G) → 6A1(6S) of Fe3+ centre in ZnO reveal the trigonal symmetry of fine structure of lowest Γ8 (4T1) excited state. The studies were performed in external magnetic fields up to 10 T and in the temperature range from 2 to 30 K. The energy positions of the Zeeman components at 8 T were measured as a function of the direction of applied magnetic field in $(1\bar {2}10)$ and (0001) planes. The detailed check of the angular variation of Zeeman lines shows two magnetically non‐equivalent Fe3+ centres. These special features were accounted by contribution of higher rank Zeeman terms of dimension BJ3. The photo‐generated EPR spectra of trigonal Fe3+ centres were detected in hydrothermally grown ZnO single crystals in addition to three types of charge compensated iron centres presented in these samples in the dark conditions.