Publication Details

Chatzichristos, A., McFadden, R. M. L., Karner, V. L., Cortie, D. L., Levy, C. D. P., MacFarlane, W. A., Morris, G. D., Pearson, M. R., Salman, Z. & Kiefl, R. F. (2018). Comparison of 8Li and 9Li spin relaxation in SrTiO3 and Pt: A means to distinguish magnetic and electric quadrupolar sources of relaxation. Proceedings of the 14th International Conference on Muon Spin Rotation, Relaxation and Resonance (μSR2017) (pp. 011048-1-011048-9). Tokyo, Japan: The Physical Society of Japan.


We demonstrate that the ratio of 1/T1 spin-lattice relaxation rates (SLR) of two different isotopes (here 8Li and 9Li) can be used in order to identify the predominant relaxation mechanism within the β-NMR technique. We studied with both isotopes a Pt foil and two samples of single crystal SrTiO3. In Pt, the ratio of the SLR rates was 6.82(29), which is close to but less than the theoretical limit of ∼7.68 for pure magnetic relaxation. In SrTiO3, the weighted averaged SLR ratio of the two samples was 2.7(3), which is close but larger than the theoretical limit of ∼2.14 expected for pure electric quadrupolar relaxation. This indicates that the primary source of relaxation in SrTiO3 is electric quadrupolar in origin and that magnetic effects have a much smaller importance in this material. The low effective asymmetry of 9Li was the dominant cause of uncertainty of the measurements in this study. We propose a system of tagging the beta-decays in coincidence with the alpha decays that take place in two of the three primary decay channels of 9Li as a way of increasing the effective asymmetry and enhance the signal of 9Li β-NMR.



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