Physical Review B - Up to Vol 78 No 12

Nuclear magnetic resonance linewidth and spin diffusion in 29Si isotopically controlled silicon
Hiroshi Hayashi, Kohei M. Itoh and Leonid S. Vlasenko
Phys. Rev. B 78, 153201 (2008)
A nuclear magnetic resonance (NMR) study was performed with n-type silicon single crystals containing 29Si isotope abundance f ranges from 1.2% to 99.2%. The nuclear spin diffusion coefficient D has been determined from the linewidth of significantly enhanced 29Si NMR signals utilizing a developed dynamic nuclear polarization (DNP) method. The 29Si NMR linewidth depends linearly on f, at least when f<10%, and approaches f1/2 dependence when f>50%. The estimated 29Si nuclear spin diffusion time Tsd between phosphorus atoms used for DNP is more than ten times shorter than the nuclear polarization time T of 29Si nuclei around phosphorus. Therefore, the regime of “rapid spin diffusion” is realized in the DNP experiments.

Magnetization and Cu nuclear magnetic resonance study of Sr0.9La0.1Cu1−xNixO2
G. V. M. Williams, S. Richter, J. Haase, C. U. Jung, Hye-Gyong Lee, and Sung-Ik Lee
Phys. Rev. B 78, 104522 (2008)
We report the results from a Cu nuclear magnetic resonance (NMR) and magnetization study of the electron-doped high-temperature superconducting cuprate (HTSC) Sr0.9La0.1Cu1−xNixO2. This compound shows a large suppression of superconductivity by Ni [Tc/x=18 K/%(Ni)] that is comparable to that observed in underdoped and hole-doped HTSCs. We find small effective moments of 0.06µB/Cu for the pure sample and 0.76µB/Ni for the 1% Ni sample in the paramagnetic regime. The partial substitution of Ni for Cu causes the Cu NMR linewidth to increase and there is a further reduction in the Cu NMR intensity with decreasing temperature over and above that observed in the pure compound. This can be interpreted in terms of Ni inducing additional spin disorder and wipeout of the Cu NMR intensity for Cu sites near the Ni impurities.

19F NMR investigation of the iron pnictide superconductor LaFeAsO0.89F0.11
K. Ahilan, F. L. Ning, T. Imai, A. S. Sefat, R. Jin, M. A. McGuire, B. C. Sales, and D. Mandrus
Phys. Rev. B 78, 100501(R) (2008)
We report on 19F nuclear magnetic resonance (NMR) investigation of the high-temperature superconductor LaFeAsO0.89F0.11 (Tc~28 K). We demonstrate that low-frequency spin fluctuations exhibit pseudogap behavior above Tc. We also deduce the London penetration depth from NMR line broadening below Tc.

Atomic-scale measurement of ultraslow Li motions in glassy LiAlSi2O6 by two-time 6Li spin-alignment echo NMR correlation spectroscopy
M. Wilkening, A. Kuhn, and P. Heitjans
Phys. Rev. B 78, 054303 (2008)
6Li spin-alignment echo (SAE) nuclear-magnetic-resonance (NMR) spectroscopy is used to monitor single-particle two-time correlation functions in LiAlSi2O6 glass. The method, here applied in the temperature range from 300 to 400 K, is sensitive to ultraslow Li hopping processes with rates (1/SAE) down to 10 jumps/s. The use of a sample with natural 6Li abundance allowed the measurement of pure NMR spin-alignment echoes which are damped with increasing mixing time exclusively by slow Li jumps, i.e., free of influences arising from, e.g., interfering spin-diffusion effects. The considerably stretched correlation functions reveal the presence of a broad distribution of jump rates. The results are comprehensively compared with those recently obtained from both 7Li SAE and 7Li spin-lattice relaxation NMR as well as from dc conductivity measurements. Interestingly, the activation energy of the latter, which are sensitive to long-range Li transport parameters, is in good agreement with that microscopically probed by 6Li SAE NMR, here.