We show by inelastic neutron scattering that dynamic spin correlations coexist with superconductivity in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{6+\mathit{x}}$ (x=0.4,0.45,0.5). For the x=0.5, ${\mathit{T}}_{\mathit{c}}$=50 K sample, the inelastic magnetic intensity at ΔE=6 meV does not show any change near ${\mathit{T}}_{\mathit{c}}$ and is approximately constant from 250 to 10 K, in contrast to earlier data on superconducting ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{CuO}}_4$ (${\mathit{T}}_{\mathit{c}}$=35 K) which showed a decrease of the integrated intensity at a temperature well above ${\mathit{T}}_{\mathit{c}}$. The inelastic magnetic cross section observed here can be consistently modeled as two-dimensional spin waves overdamped by short correlation lengths. The correlation length in the x=0.5 sample is an order of magnitude smaller than in the x=0.40 and x=0.45 samples, indicating a drastic disruption of planar copper spin-spin correlation upon hole doping. The present results are compared with recent NMR studies of ${\mathit{T}}_{\mathit{c}}$=60 K material.

• Received 12 December 1990

DOI:https://doi.org/10.1103/PhysRevB.43.5554