Q. Song

β-NMR of isolated lithium in nearly ferromagnetic palladium

The temperature dependence of the frequency shift and spin-lattice relaxation rate of isolated, nonmagnetic (8)Li impurities implanted in a nearly ferromagnetic host (Pd) are measured by means of beta-detected nuclear magnetic resonance (beta-NMR). The shift is negative, very large, and increases monotonically with decreasing T in proportion to the bulk susceptibility of Pd for T > T* approximately 100 K. Below T*, an additional shift occurs which we attribute to the response of Pd to the defect. The relaxation rate is much slower than expected for the large shift and is linear with T below T*, showing no sign of additional relaxation mechanisms associated with the defect.

Search for broken time-reversal symmetry near the surface of superconducting YBa2Cu3O7-δ films using β-detected nuclear magnetic resonance

H. Saadaoui, ∗ G. D. Morris, Z. Salman, ∗ Q. Song, K. H. Chow, M. D. Hossain, C. D. P. Levy, T. J. Parolin, M. R. Pearson, M. Smadella, D. Wang, L. H. Greene, P. J. Hentges, R. F. Kiefl, 2, 7 and W. A. MacFarlane Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada Clarendon Laboratory, Department of Physics, Oxford University, Parks Road, Oxford, OX1 3PU, UK Department of Physics, University of Alberta, Edmonton, AB, T6G 2G7, Canada Chemistry Department, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61801, USA Canadian Institute for Advanced Research, Toronto, ON, M5G 1Z8, Canada (Dated: January 6, 2011)

Nuclear electric quadrupole moment of 9Li using zero-field β-detected NQR

A ?-detected nuclear quadrupole resonance (NQR) spectrometer becomes a powerful tool to study changes in nuclear ground-state properties along isotopic chains when coupled to a laser excitation beamline to polarize the nuclei of interest. Recently, the ?-NQR technique in a zero magnetic field has been applied for the first time to measure the ratio of static nuclear quadrupole moments of 8, 9Li, Q9/Q8 = 0.966?75(9) denoted by Q8 for 8Li and Q9 for 9Li, respectively. This shows agreement with present literature values but with significantly improved precision. Based on the literature, the quadrupole moment for 8Li has been re-evaluated to be |Q8| = 32.6(5)?mb. From this, the quadrupole moment for 9Li is calculated as |Q9| = 31.5(5)?mb with the error being dominated by the error of Q8.

High precision measurement of the 11Li and 9Li quadrupole moment ratio using zero-field β-NQR

The ratio of electric quadrupole moments of 11 Li and 9 Li was measured using the zero-field β-detected nuclear quadrupole resonance technique at TRIUMFISAC. The precision on the ratio Q11/Q9 = 1.0775(12) was improved by more than one order of magnitude and an absolute value for the quadrupole moment of 11 Li was inferred. Systematic effects, as argued here, are not expected to contribute to the ratio on this scale. The zero-field spin-lattice relaxation time for 8 Li implanted within SrTiO3 at 295K in zero-field was found to be T1 = 1.73(2)s. A comparison of the quadrupole moments of 9,11 Li and their ratio is made with the latest models, however, no conclusion may yet be drawn owing to the size of the theoretical uncertainties.

Vortex lattice disorder inYBa2Cu3O7−δprobed usingβ-NMR

Beta-NMR has been used to study vortex lattice disorder near the surface of the high-Tc superconductor YBCO. The magnetic field distribution from the vortex lattice was detected by implanting a low energy beam of highly polarized 8Li into a thin overlayer of silver on optimally doped, twinned and detwinned YBCO samples. The resonance in Ag broadens significantly below the transition temperature Tc as expected from the emerging field lines of the vortex lattice in YBCO. However, the lineshape is more symmetric and the dependence on the applied magnetic field is much weaker than expected from an ideal vortex lattice, indicating that the vortex density varies across the face of the sample, likely due to pinning at twin boundaries. At low temperatures the broadening from such disorder does not scale with the superfluid density.

Slow order-parameter fluctuations in superconducting Pb and Ag/Nb films observed usingβ-detected nuclear magnetic resonance

E. Morenzoni, ∗ H. Saadaoui, D. Wang, M. Horisberger, E. Kirk, W.A. MacFarlane, G. D. Morris, K.H. Chow, M.D. Hossain, C.P. Levy, T.J. Parolin, M.R. Pearson, Q. Song, and R. F. Kiefl 6 Paul Scherrer Institut, Laboratory for Muon Spin Spectroscopy, 5232 Villigen PSI, Switzerland Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada, V6T Paul Scherrer Institut, Laboratory for Developments and Methods, 5232 Villigen PSI, Switzerland Paul Scherrer Institut, Labor für Mikround Nanotechnologie, CH-5232 Villigen PSI, Switzerland Chemistry Department, University of British Columbia, Vancouver, BC, Canada, V6T 1Z1 TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, Canada, V6T 2A3 Department of Physics, University of Alberta, Edmonton, AB, Canada, T6G 2G7 (Dated: September 22, 2011)

8Li β-NMR study of epitaxial LixCoO2 films

In order to investigate the diffusive motion of Li+ in a thin film electrode material for Li-ion batteries, we have measured β-NMR spectra of 8Li+ ions implanted into epitaxial films of Li0.7CoO2 and LiCoO2 in the temperature range between 10 and 310 K. Below 100 K, the spin-lattice relaxation rate (1/T1) in the Li0.7CoO2 film increased with decreasing temperature, indicating the appearance and evolution of localized magnetic moments, as observed with μ+SR. As temperature is increased from 100 K, 1/T1 starts to increase above ~ 200 K, where both Li- NMR and μ+SR also sensed an increase in 1/T1 due to Li-diffusion. Interestingly, such diffusive behavior was found to depend on the implantation energy, possibly because the surface of the film is decomposed due to chemical instability of the Li0.7CoO2 phase in air. Such diffusive behavior was not observed for the LiCoO2 film up to 310 K.

The development of pure β-NQR techniques for measurements of nuclear ground state quadrupole moments in lithium isotopes

A β-NQR spectrometer becomes a powerful tool to study changes in nuclear ground state properties along isotopic chains when coupled to a laser excitation beamline to polarise the nuclei of interest. Recently, the β-NQR technique in a zero magnetic field has been applied for the first-time to measure ratios of static nuclear quadrupole moments of, Li. Preliminary results of the experiment determining the ratios Q9/Q8 and Q11/Q9 show agreement with present literature values with improved precision.