  Magnetic excitations in CuCrO$_{2}$, CuCr$_{0.97}$Mg$_{0.03}$O$_{2}$,
Cu$_{0.85}$Ag$_{0.15}$CrO$_{2}$, and CuCr$_{0.85}$Al$_{0.15}$O$_{2}$ have been
studied by powder inelastic neutron scattering to elucidate the element
substitution effects on the spin dynamics in the Heisenberg triangular-lattice
antiferromagnet CuCrO$_{2}$. The magnetic excitations in
CuCr$_{0.97}$Mg$_{0.03}$O$_{2}$ consist of a dispersive component and a flat
component. Though this feature is apparently similar to CuCrO$_{2}$, the energy
structure of the excitation spectrum shows some difference from that in
CuCrO$_{2}$. On the other hand, in Cu$_{0.85}$Ag$_{0.15}$CrO$_{2}$ and
CuCr$_{0.85}$Al$_{0.15}$O$_{2}$ the flat components are much reduced, the
low-energy parts of the excitation spectra become intense, and additional
low-energy diffusive spin fluctuations are induced. We argued the origins of
these changes in the magnetic excitations are ascribed to effects of the doped
holes or change of the dimensionality in the magnetic correlations.
