Neutron-scattering study of magnetic fluctuations in Zn-substituted ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{6.6}$

Inelastic-neutron-scattering measurements of magnetic fluctuations in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_{2.9}$${\mathrm{Zn}}_{0.1}$${\mathrm{O}}_{6.6}$ as a function of temperature are presented. In this nonsuperconducting sample magnetic fluctuations at (π,π) are observed at all temperatures (10<T<200 K) and energies (2<E<12 meV) studied in the experiment. This finding should be contrasted to the situation in pure, superconducting ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{6.6}$, where the low-energy (E<5 meV) spin fluctuations are suppressed at low temperature leading to gaplike behavior.