Electron spin resonance linewidths of Co2+ in magnesium oxide |
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Authors: | J. S. Thorp M. D. Hossain L. J. C. Bluck T. G. Bushell |
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Affiliation: | (1) Department of Applied Physics and Electronics, University of Durham, UK;(2) Present address: Clarendon Laboratory, Parks Road, Oxford, UK |
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Abstract: | Electron spin resonance linewidths of Co2+ in single-crystal MgO at 9 GHz were examined experimentally and theoretically for a range of Co2+ concentration from 310 to 9900 ppm. In contrast to the behaviour expected from dipolar broadening, the experimental peak-to-peak linewidth for the octed hyperfine lines were about twelve to fifty times less than the calculated dipolar linewidths according to temperature and concentrations. The peak-to-peak linewidths as determined experimentally increase from 0.8 mT at 310 ppm Co2+ to 4.0 mT at 9900 ppm Co2+ at a polar angle H= O° and at 20 K. Peak-to-peak linewidths independent of polar angle but strongly dependent on temperature and slightly dependent on concentrations were observed. The ratio of moments M41/4/M21/2derived from the experimental data lay between 1.35 to 1.44 and the lineshapes were markedly Lorentzian in the range of temperature measured. The data suggest that Co2+ entered the lattice substitutionally, occupying magnesium sites, that the linewidths were determined, after exchange energy, over the whole concentration range examined and that the exchange energy whose values lay between 6 and 77 GHz, varied linearly with concentration. |
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