Partially disordered spin structure in Ag2CrO2 studied with mu+SR
The magnetism of a metallic two-dimensional triangular antiferromagnetic (AF) compound, Ag2CrO2, has been investigated by muon-spin rotation and relaxation (mu+SR) using a powder sample in the temperature range between 1.8 and 40 K. Below T-N = 24 K, a muon-spin precession signal was clearly observed in the zero-field spectrum, indicating the formation of static AF order. It was also found that the internal field is temperature independent except for in the vicinity of T-N, as in the case for the susceptibility versus temperature curve. This suggests that the AF transition is induced by a first-order structural phase transition at T-N. Combining the mu+SR result with the prediction for muon sites in the lattice by first-principles calculations, a partially disordered AF state was found to be the most reasonable spin structure for Ag2CrO2.