High field ESR measurement of CsCuCl3 near the commensurate-incommensurate transition

High field ESR of triangular antiferromagnet CsCuCl3 has been performed in the wide frequency region from 50 to 590 GHz at 4.2 K. The system is in an incommensurate helical structure along the chain direction (c-axis) at 4.2 K and zero field, and the transverse pulsed magnetic field (H//a) up to 23 T has been applied. Detailed frequency dependence measurements revealed that the weak minor absorption lines tend to zero GHz at 17 T. Moreover, although the resonance field of the strong major absorption line shows no anomaly at 17 T, the broadening of the major absorption line was observed above 17 T for the first time. This field is consistent with the incommensurate-commensurate transition observed in the recent high field neutron diffraction measurement by Nojiri et al. up to 25 T. (author)