Impurity effects on the Ni3+ triangular lattice of Ag2NiO2

Silver oxonickelate Ag2NiO2 is a metallic compound presenting a spin-1/2 triangular lattice. It exhibits a structural transition at Ts = 260 K, which may be related to eg orbital ordering, and an antiferromagnetic transition at TN = 55 K. Impurity effects on its magnetic and electronic properties are examined by substituting Fe for Ni in Ag2Ni1−xFexO2 (0≤x≤0.3). A Curie-like enhancement in magnetic susceptibility is observed at low temperature, which implies that most Fe3+ spins behave as free spins. Moreover, a large enhancement of residual resistivity and its suppression under magnetic fields are observed. Magnetic interactions in the Ni3+ triangular lattice are discussed.