Negative magnetization of Li2Ni2Mo3O12 having a spin system composed of   distorted honeycomb lattices and linear chains
  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. 
Masashi Hase, Vladimir Yu. Pomjakushin, Vadim Sikolenko, Lukas Keller,   Hubertus Luetkens, Andreas Doenni, and Hideaki Kitazawa
cond-mat.str-el