Electron-spin-resonance study of Tl atom defects in KCl and relativistic many-body analysis of the hyperfine structure
- 1 July 1981
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 24 (1), 29-50
- https://doi.org/10.1103/physrevb.24.29
Abstract
Two thallium atom defects of tetragonal symmetry around are produced by x irradiation above 230 K in KCl: TlCl. Their electron-spin-resonance spectra are characterized by comparable and large shifts but quite different hyperfine parameters. A relativistic many-body calculation of the atom hyperfine interaction including the effect of a tetragonal crystal field permits a quantitative analysis of the spin-Hamiltonian parameters. It is found in particular that the hyperfine data of the two defects can be explained by assuming the presence of one or two perturbing positive charges, respectively, and a corresponding 35 and 45% delocalization of the electron on the surrounding lattice. This analysis together with x-ray production, optical-excitation, and pulse-anneal data and the fact that both defects can only be produced at temperatures where negative-ion vacancies are mobile (>230 K) allows one to propose precise defect structures: In one defect the atom (on a positive-ion site) is associated with a single negative-ion vacancy in a nearest-neighbor position along ; in the other one, the is flanked by two nearest-neighbor negative-ion vacancies along . The data also provide strong evidence for the existence of a defect consisting of a ion and a nearest-neighbor anion vacancy.
Keywords
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