Spin-Lattice Relaxation of Pairs of Chromium Ions in Ruby


THE electron paramagnetic resonance spectrum of ruby contains many weak lines as well as those of single chromium ions. It has been established from the dependence of their intensity on the chromium concentration that most of these arise from pairs of ions. An example of the ‘pair’ spectrum is given in Fig. 1. A complete analysis is hot available, but Rimai et al. have identified the lines due to nearest-neighbour pairs, and find an antiferromagnetic exchange interaction JS 1.S 2 with J = 250 cm.−1, to be present1. These pairs are not observed at low temperatures, being then almost all in their singlet ground-state. Most of the lines, however, come from more widely separated ions, and many persist even at 1.3° K. The variation of their intensities with temperature indicates that levels separated from the ground-state by 0–15 cm.−1 are present.

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  1. 1

    Rimai, L., Statz, H., Weber, M. J., de mars, G. A., and Koster, C. F., Phys. Rev. Letters, 4, 125 (1960).

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    Finn, C. P. B., Orbach, R., and Wolf, W. P., Proc. Phys. Soc. (in the press).

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    Van Vleck, J. H., Quantum Electronics, 392 (Columbia University Press, 1960).

  4. 4

    Mims, W. B., and McGee, J. D., Phys. Rev., 119, 1233 (1960).

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GILL, J. Spin-Lattice Relaxation of Pairs of Chromium Ions in Ruby. Nature 190, 619–620 (1961). https://doi.org/10.1038/190619a0

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