Optical Spectroscopy on Triangular Lattice Antiferromagnets

Antiferromagnetically coupled spins on a triangular lattice can result due to the inherent frustration of the system in exotic ground states and consequently in an exotic excitation spectrum. In this work the magnetic excitations of the three triangular lattice antiferromagnets CuCrO2, NaCrO2, and alpha-CaCr2O4 and their temperature dependence are investigated by means of THz-time domain spectroscopy and Fourier-Transform Infrared spectroscopy. The exciton-magnon excitations, antiferromagnetic resonances, and phonons we found in these compounds are ideal to search for short range correlations above the magnetic ordering temperature, for the influence of possible topological defects, and for the existence of two-magnon bound states.