Ferrodistorsive orbital ordering in the layered nickelate NaNiO2: A density-functional study

Abstract

The electronic structure and magnetism in the sodium nickelate NaNiO2 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 0.7μB 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.