Using Ni Substitution and17ONMR to Probe the Susceptibilityχ′(q)in Cuprates

Abstract

We present ${\mathrm{CuO}}_2$ plane ${}^{17}\mathrm{O}$ NMR measurements for Ni-substituted ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{6+y}$. The Ni moment induces an oscillatory spin density responsible for the broadening of the NMR line. In slightly overdoped $y=1\mathrm{}$ compounds, this broadening scales with the Ni susceptibility. In contrast, such a scaling is not found in underdoped $y=0.6\mathrm{}$ samples. We associate it with the T dependence of the antiferromagnetic staggered spin susceptibility ${\chi }^{\prime }\left({\mathbf{Q}}_{\mathrm{AF}}\right)$ intrinsic to the ${\mathrm{CuO}}_2$ planes. Discussion with respect to ${}^{63}\mathrm{Cu}$ NMR transverse relaxation ( $T_{2G}$) and neutron scattering data shows that the AF correlation length $\xi$ is T independent.