Magnetic excitations in \srruo ~ have been studied by inelastic neutron
scattering. The magnetic fluctuations are dominated by incommensurate peaks
related to the Fermi surface nesting of the quasi-one-dimensional dxz- and
dyz-bands. The shape of the incommensurate signal agrees well with RPA
calculations. At the incommensurate {\bf Q}-positions the energy spectrum
considerably softens upon cooling pointing to a close magnetic instability :
\srruo ~does not exhibit quantum criticality but is very close to it. ω/T-scaling may be fitted to the data for temperatures above 30 K. Below the
superconducting transition, the magnetic response at the nesting signal is not
found to change in the energy range down to 0.4meV.Comment: 11 pages 9 figure