O17NMR Study of the Intrinsic Magnetic Susceptibility and Spin Dynamics of the Quantum Kagome AntiferromagnetZnCu3(OH)6Cl2

We report, through ${}^{17}\mathrm{O}$ NMR, an unambiguous local determination of the intrinsic kagome lattice spin susceptibility as well as that created around nonmagnetic defects arising from natural $\mathrm{Zn}/\mathrm{Cu}$ exchange in the $S=1/2$ (${\mathrm{Cu}}^{2+}$) herbertsmithite ${\mathrm{ZnCu}}_3(\mathrm{OH}{)}_6{\mathrm{Cl}}_2$ compound. The issue of a singlet–triplet gap is addressed. The magnetic response around a defect is found to markedly differ from that observed in nonfrustrated antiferromagnets. Finally, we discuss our relaxation measurements in the light of Cu and Cl NMR data and suggest a flat $q$ dependence of the excitations.