O17 NMR Study of q=0 Spin Excitations in a Nearly Ideal S=12 1D Heisenberg Antiferromagnet, Sr2CuO3, up to 800 K

We used 17O 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 approximately 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<