Quadrupolar split -NMR in SrTiO3

Nuclear magnetic resonance study of Li implanted in a thin film of niobium

“…8 Li's small Q yields small quadrupole splittings typically in the range of 10-100 kHz in insulators. 20,21 Interestingly, the splitting in Nb ͑ϳ50 kHz͒ is also on this order. This measurement of the EFG will provide an important test for modern calculations of hyperfine interactions in metals.…”

“…29 Due to the high polarization of the 8 Li nuclei, predominantly the m =2 ͑−2 for the opposite helicity͒ state is populated initially, so we expect only the outermost satellite transition 2 ↔ 1͑−2 ↔ −1͒ to be evident in the spectrum as was seen in, e.g., SrTiO 3 . 21 By symmetry, for both O and T sites, the principal z axis of the EFG is along a ͗100͘ direction. 25 The applied field in the ͗110͘ direction breaks the symmetry, yielding two angles = 45°and 90°in a 2:1 intensity ratio.…”

β-NMR of 8Li+ in rutile TiO2

“…From the combined asymmetry (A), we find a broad, 12.48 ± 0.12 kHz wide quadrupole split resonance with unresolved features. This is in stark contrast to the 8 Li + resonance in Bi, where the four quadrupole satellite and three double-quantum transitions are well-resolved, 2 or in the perovskite SrTiO 3 , where the satellite splitting is greater by about an order of magnitude [17]. X-ray diffraction and reflectometry measurements do not reveal the presence of impurity phases, though static disorder (e.g., from oxygen vacancies, as indicated by the discolouration of the crystal, or transition metal impurities) is a possible cause for the broadening.…”

“…1-3 to the slr spectra in Figure 3 = 0.141 ± 0.005 s −1 . Such a relaxation rate is relatively high compared to other insulating metal oxides [17], where 8 Li + can be nearly non-relaxing. 1 As rutile is non-cubic and virtually without nuclear moments ( 47 Ti: I = 3/2, 7.28%; 49 Ti: I = 5/2, 5.51%, 17 O: I = 5/2, 0.038%), it is likely that the relaxation is predominantly quadrupolar in nature.…”

“…The asymmetric time-integrated asymmetries from spin-polarization with different helicities (A ± ) are characteristic of a quadrupole split resonance [17,19]. From the combined asymmetry (A), we find a broad, 12.48 ± 0.12 kHz wide quadrupole split resonance with unresolved features.…”