Substitution effects on ferromagnetic Mott insulator Lu2V2O7 Original Research Article

A model is proposed for the ferromagnetism of a Mott insulator Lu2V2O7. In relation to this model, substitution effects of Ti and Nb atoms for V atoms in Lu2V2O7 have been studied, where all ions are found to have valence of +4, i.e. S=1/2 for V4+, S=0 for Ti4+ and S=1/2 for Nb4+ as a localized spin by studying their lattice parameters and Curie constants. Saturated magnetic moments in Lu2V2−xNbxO7 system are smaller than paramagnetic moments in Curie–Weiss law, indicating spin canting or anisotropy. Its effect on Curie temperature Tc corresponds to the decrease of mean magnetic moments along the magnetic field, while the effect of Ti substitution on Tc is explained by the decrease of number of the nearest neighbor spins. These substitution effects on Tc do not contradict the present model.