Effects of Mg, Ag, and Al Substitutions on Magnetic Excitations in the Triangular-Lattice Antiferromagnet CuCrO2

Magnetic excitations in CuCrO2, CuCr0.97Mg0.03O2, Cu0.85Ag0.15CrO2, and CuCr0.85Al0.15O2 have been studied by powder inelastic neutron scattering to elucidate the element substitution effects on spin dynamics in the Heisenberg triangular-lattice antiferromagnet CuCrO2. Magnetic excitations in CuCr0.97Mg0.03O2 consist of a dispersive component and a flat component. Although this feature is apparently similar to that observed in CuCrO2, the energy structure of the excitation spectrum shows some difference from that of the excitation spectrum of CuCrO2. On the other hand, in Cu0.85Ag0.15CrO2 and CuCr0.85Al0.15O2, flat components are much suppressed, the low-energy parts of the excitation spectra become intense, and additional low-energy diffusive spin fluctuations are induced. We argued that the origins of these changes in the magnetic excitations are the effects of doped holes or the change in dimensionality in magnetic correlations.