Static magnetic order on the triangular lattice in LixNiO2LixNiO2 with x⩽1x⩽1

In spite of numerous experimental and theoretical reports on LiNiO2LiNiO2, due to fundamental interest because its Ni3+Ni3+ ions form a triangular S=12 two-dimensional lattice, no consistent picture has emerged of the nature of its ground state. We have investigated the LixNiO2LixNiO2 system (0.1⩽x⩽1)(0.1⩽x⩽1) using muon-spin spectroscopy to gain further insight from the effects of varying the spin concentration. Static magnetic order, most likely to be incommensurate to the spatial lattice period, was found for x⩾0.6x⩾0.6, while disordered magnetism due to localized Ni moments appears for x=12-14, and, finally, Li0.1NiO2Li0.1NiO2 exhibits almost fully non-magnetic behavior. Combining the result of susceptibility measurements, the ground state of LiNiO2LiNiO2 is thought to be a “static but short-range” A-type antiferromagnetic ordered system. That is, the Ni3+Ni3+ moments align ferromagnetically along the c  -axis in the NiO2NiO2 plane with an incommensurate modulation probably due to canting of the Ni3+Ni3+ moments, but antiferromagnetically between the adjacent NiO2NiO2 planes.