The influence of water-immersing on the magnetic behaviorof Rb2Ni3S4 single crystals grown by the fluxmethod was studied, where the intrinsic substance is non-magnetic because of thelow spin state of Ni2+ in a Kagome lattice. The influence ofCo-doping to Rb2Ni3S4 was also studied in termsof the local spin density approximation (LSDA) band structure calculation.Residual ferromagnetic moments appeared in specimens immersed into water, astheir magnitudes increase depending on the immersion time. The LSDA bandstructure calculation suggested that Co substitution for Ni allows deriving anovel ferromagnetic behavior.
