NMR investigation on quasi-one-dimensional purple bronze Li$_{0.9}$Mo$_{6}$O$_{17}$

$^{7}$Li-NMR measurements are reported for a single crystal of quasi-1D conductor Li$_{0.9}$Mo$_{6}$O$_{17}$ (lithium purple bronze) as a function of temperature ($\it{T}$) and applied magnetic field ($B_{0}$). The $^{7}$Li-NMR spin-lattice relaxation rate (1/$T_{1}$) follows a Korringa relation above $\sim$ 50 K and has surprising features at lower $T$ with 6T$\leq$ B$_{0}$$\leq$12 T. This behavior indicates a conventional electron motion in the high $T$ metallic state with a change at lower $T$ in the electron density of states and perhaps the correlation time. A similar behavior is also shown by $^{95}$Mo 1/$T_{1}$ measurements made at 14.8 T. The $^{7}$Li-NMR spectra also show a significant inhomogeneous broadening and frequency shift across the temperature ($T_{min}$) where the resistivity exhibits a minimum. This indicates a substantial local field change below $T_{min}$. A possible scenario for the development of a field induced spin-density wave state is discussed. Noticeably, these are challenging experiments due to the long $^{7}$Li spin- lattice relaxation time ($T_{1}$) and small natural abundance of $^{95} $Mo in the material. It is the first reported NMR measurement for the material. This work was supported at UCLA by NSF Grants DMR-0334869 and DMR-0520552, and at MSU by NSF Grant DMR-0907036.