  Spin fluctuations of the archetypal heavy-fermion compound CeRu_2Si_2 have
been investigated by neutron scattering in an entire irreducible Brillouin
zone. The dynamical susceptibility is remarkably well described by the
self-consistent renormalization (SCR) theory of the spin fluctuation in a
phenomenological way, proving the effectiveness of the theory. The present
analysis using the SCR phenomenology has allowed us to determine fourteen
exchange constants, which show the long-range nature of the
Ruderman-Kittel-Kasuya-Yosida interaction.
