Antiferromagnetic insulating state in layered nickelates at half filling

We provide a set of computational experiments based on ab initio calculations to elucidate whether a cuprate-like antiferromagnetic insulating state can be present in the phase diagram of the low-valence layered nickelate family (R_n+1Ni_nO_2n+2, R= rare-earth, n = 1−∞) in proximity to half-filling. It is well established that at d⁹ filling the infinite-layer (n = ∞) nickelate is metallic, in contrast to cuprates wherein an antiferromagnetic insulator is expected. We show that for the Ruddlesden-Popper (RP) reduced phases of the series (finite n) an antiferromagnetic insulating ground state can naturally be obtained instead at d⁹ filling, due to the spacer RO₂ fluorite slabs present in their structure that block the c-axis dispersion. In the n = ∞ nickelate, the same type of solution can be derived if the off-plane R-Ni coupling is suppressed. We show how this can be achieved if a structural element that cuts off the c-axis dispersion is introduced (i.e. vacuum in a monolayer of RNiO₂, or a blocking layer in multilayers formed by (RNiO₂)₁/(RNaO₂)₁).