17O NMR study of q=0 spin excitations in a nearly ideal S=1/2 1D Heisenberg antiferromagnet, Sr2CuO3, up to 800 K -: art. no. 247202

We used O-17 NMR to probe the uniform (wave vector q = 0) electron spin excitations up to 800 K in Sr2CuO3 and separate the q = 0 from the q = +/- pi /a staggered components. Our results support the logarithmic decrease of the uniform spin susceptibility below T similar to 0.015J, where J = 2200 K. From measurement of the dynamical spin susceptibility for q = 0 by the spin-lattice relaxation rate 1/T-1, we demonstrate that the q = 0 mode of spin transport is ballistic at the T = 0 limit, but has a diffusion-like contribution at finite temperatures even for T << J.