  We study themagnetism of a spin-1 substance Li2Ni2Mo3O12. The spin system
consists of distorted honeycomb lattices and linear chains of Ni2+ spins. Li+
ions enter about 25% and 50% of the honeycomb and chain Ni sites, respectively,
creating disorder in both spin subsystems. A magnetic phase transition occurs
at Tc = 8.0 K in the zero magnetic field. In low magnetic fields, the
magnetization increases rapidly below Tc, decreases below 7 K, and finally
becomes negative at low temperatures. We determine the magnetic structure using
neutron powder diffraction results. The honeycomb lattices and linear chains
show antiferromagnetic and ferromagnetic long-range order, respectively. We
investigate static and dynamic magnetic properties using the local probe
technique of muon spin relaxation. We discuss the origin of the negative
magnetization.
