Anomalous magnetic excitation on triangular lattice antiferromagnet CuFeO2

Abstract The magnetic excitation spectrum has been investigated by inelastic neutron scattering on triangular lattice antiferromagnets CuFeO 2 and CuFe 0.98 Al 0.02 O 2 . While the normal acoustic spin-wave dispersion curve was obtained in CuFe 0.98 Al 0.02 O 2 , the anomalous dispersion curve with energy gap whose bottom positions do not correspond to the magnetic Bragg point for the 4-sublattice (↑↑↓↓) ground state was obtained in CuFeO 2 .