Ferrodistorsive orbital ordering in the layered nickelate NaNiO_2: A density-functional study

TL;DR

This study uses density-functional calculations to investigate the electronic structure and magnetic properties of NaNiO_2, revealing ferrodistorsive orbital ordering and specific magnetic interactions consistent with experimental observations.

Contribution

It provides a detailed density-functional analysis of orbital ordering and magnetic interactions in NaNiO_2, highlighting the role of Jahn-Teller distortion and superexchange pathways.

Findings

Ferrodistorsive orbital ordering due to Jahn-Teller distortion.

Intralayer ferromagnetic exchange.

Weak interlayer antiferromagnetic exchange.

Abstract

The electronic structure and magnetism in the sodium nickelate NaNiO_2 in the low-temperature phase is studied from density-functional calculations using the linear muffin-tin orbitals method. An antiferromagnetic solution with a magnetic moment of 0.7 m_B per Ni ion is found. A ferrodistorsive orbital ordering is shown to occur due to the Jahn-Teller distortion around the Ni^{3+} ion in agreement with the orbital ordering inferred from neutron diffraction. While the intralayer exchange is ferromagnetic, the interlayer exchange is weakly antiferromagnetic, mediated by a long Ni-O-Na-O-Ni superexchange path.