Antiferromagnetic correlations in the metallic strongly correlated transition metal oxide LaNiO3

The material class of rare earth nickelates with high Ni 3+ oxidation state is generating continued interest due to the occurrence of a metal-insulator transition with charge order and the appearance of non-collinear magnetic phases within this insulating regime. The recent theoretical prediction for superconductivity in LaNiO 3 thin films has also triggered intensive research efforts. LaNiO 3 seems to be the only rare earth nickelate that stays metallic and paramagnetic down to lowest temperatures. So far, centimeter-sized impurity-free single crystal growth has not been reported for the rare earth nickelates material class since elevated oxygen pressures are required for their synthesis. Here, we report on the successful growth of centimeter-sized LaNiO 3 single crystals by the floating zone technique at oxygen pressures of up to 150 bar. Our crystals are essentially free from Ni 2+ impurities and exhibit metallic properties together with an unexpected but clear antiferromagnetic transition. The phase transitions of rare earth nickelates have attracted intensive study as they arise from the complex interplay of charge, spin and lattice degrees of freedom. Here Guo et al. present evidence that LaNiO 3 has an unanticipated magnetically ordered metallic phase.