  We have investigated magnetic excitations for a mixed phase of hidden order
(HO) and the antiferromagnetic (AF) order in U(Ru_{1-x}Rh_x)_2Si_2 (x <= 0.03)
by means of inelastic neutron scattering. The inelastic peaks observed at
Q=(1,0,0) and (1,0.4,0) in the HO phase for x=0 and 0.015 at 1.4 K are found to
be strongly reduced in the AF dominant compositions of x=0.02 and 0.03. Similar
behavior is observed as the HO is replaced by the AF order upon cooling for
x=0.02. The x-T region in which the strong reduction of inelastic peaks is
observed corresponds to the AF-rich region, indicating that the magnetic
excitations typical for the HO-phase vanish in the AF phase.
