THE NEUTRON RESPONSE IN U0.975CE0.025RU2SI2

We have carried out a neutron scattering study of the pseudo-ternary s ystem U0.975Ce0.025Ru2Si2. Elastic scattering measurements have indica ted antiferromagnetic order at wave vector Q(1) = (1, 0, 0) (mu = 0.00 6+/-0.003 mu(B) at T = 1.6 K). Our inelastic scattering investigation has been focused on the low-temperature excitations showing a dispersi ve energy Like for URu2Si2, two spin-gap minima occur at wave vectors Q(1) = (1, 0, 0) and Q(2) = (0.6, 0, 0). The substitution of Ce for U in URu2Si2 shifts the characteristic spin gap energy from 1.8 meV to 2 .4 meV at a wave vector Q(1), and from 4.5 meV to 4.0 meV at a wave ve ctor Q(2).