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+1 Ni _n O _2n+2 , R= rare-earth, n=1-∞ ) in proximity to half-filling. It is well established that at d^9 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 d^9 filling, due to the spacer RO _2 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 RNiO _2 , or a blocking layer in multilayers formed by (RNiO _2 ) _1 /(RNaO _2 ) _1 ).