NMR as a probe of incommensurate spin density waves in organic metals

The role of NMR measurements for investigating the properties of incommensurate spin density waves (ISDW) in solids is reviewed and several new measurements of these properties are presented in (TMTSF)2PF6 and the alloy (TMTSF)2(P0.5As0.5F6. These result include proton spin echo measurements of the temperature dependence of the spin density wave magnetic field, and the depinning electric field threshold and real part of the dielectric constant as a function of frequency and temperature. The relation between the spin-lattice relaxation rate and the imaginary part of the dielectric constant is presented and compared qualitatively with measurements. Measurements of the sliding SDW velocity using spin echoes and narrow band noise are reported. They show that the pinning potential period is half the wavelength of the SDW.