A Raman scattering investigation of the magnetic ordering in the two-dimensional triangular lattice antiferromagnet LiCrO2

Raman scattering experiments were performed on the two-dimensional triangular lattice antiferromagnet LiCrO2 to investigate its magnetic ordering. Besides two phonon lines which are assigned to the Eg and the A1g modes of D3d point symmetry, additional lines having broader linewidth than that of the phonon lines are observed at low temperatures. Their intensity becomes weak with increasing temperature, but they are still observable above TN=62 K, a value that was determined by neutron diffraction experiments, and only become unobservable at around 150 K. The lines are found to correspond to two-magnon lines when a 120 degrees Neel structure is assumed. A possible effect of the Z2 vortex on two-magnon lines in a two-dimensional triangular lattice Heisenberg antiferromagnet is discussed.