arXiv:cond-mat/0108272 · Physical Review Letters
O17 NMR Study of q=0 Spin Excitations in a Nearly Ideal S=12 1D Heisenberg Antiferromagnet, Sr2CuO3 , up to 800 K
Kent R. Thurber, A. W. Hunt, Takashi Imai, F. C. Chou
Abstract
We used ${}^{17}\mathrm{O}$ NMR to probe the uniform (wave vector $q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$) electron spin excitations up to 800 K in ${\mathrm{Sr}}_{2}{\mathrm{CuO}}_{3}$ and separate the $q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ from the $q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ifmmode\pm\else\textpm\fi{}\frac{\ensuremath{\pi}}{a}$ staggered components. Our results support the logarithmic decrease of the uniform spin susceptibility below $T\ensuremath{\sim}0.015J$, where $J\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2200\mathrm{K}$. From measurement of the dynamical spin susceptibility for $q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ by the spin-lattice relaxation rate ${1/T}_{1}$, we demonstrate that the $q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ mode of spin transport is ballistic at the $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ limit, but has a diffusion-like contribution at finite temperatures even for $T\ensuremath{\ll}J$.