μ+SR study on triangular antiferromagnet LiCrO2

In order to elucidate the magnetic nature of the lithium chromium dioxide LiCrO2, in which the Cr3+ ions form a two-dimensional triangular lattice in the CrO2 plane, we have performed a positive muon-spin rotation and relaxation (mu+SR) experiment using a powder sample at the temperatures below 155 K. Weak-transverse-field measurements indicated the existence of a bulk antiferromagnetic (AF) transition at T-N=61.2 K. The ZF-mu+SR measurements indicated that LiCrO2 is a pure paramagnet for T >= 62.5 K, since its internal magnetic field (H-int) can be explained by solely nuclear magnetic moments. This means that, contrary to previous suggestions by susceptibility and heat capacity measurements, no short-range order exists for T >= 62.5 K. However, ZF-mu+SR detected the change in H-int from a low-T static state to a high-T dynamic state at 115 K, most likely connected to a change in the position/motion of the Li ions.