Anomaly in the fine-structure splitting of EPR spectra of Cr (3+) centres in Tl2ZnF4 crystals

摘要

EPR measurements have been made at room temperature on as-grown single crystals of Tl2ZnF4. For crystals doped with Cr3+, signals from the Cr3+ centres with monoclinic (centre II) and orthorhombic (centre III) symmetries are observed together with ones from the uncompensated tetragonal centre (centre I). On the basis of spin-Hamiltonian separation analysis, the Centre II is ascribed to a Cr3+ ion substituted for a Zn2+ site with a vacancy at its nearest Tl+ site. The centre III is ascribed to a Cr3+ ion associated with a vacancy at the nearest Zn2+ site. Anomalies were revealed in the separated parameters b(2a(1)) for the centres II, III and in b(2a(2)) for the centre III, which have about double the magnitude of those in the other layered perovskite fluorides Rb2ZnF4, K2ZnF4 with different monovalent cations. These anomalies may be due to some effect of the nearest and the next-nearest Tl+ ions. [References: 14]