The effect of octahedral distortions on the electronic properties and magnetic interactions in O3 NaTMO 2 compounds (TM = Ti-Ni & Zr-Pd).

The interplay between the coordination environment and magnetic properties in O3 layered sodium transition metal oxides (NaTMO 2 ) is a fascinating and complex problem. Through detailed and comprehensive density functional investigations on O3 NaTMO 2 compounds, we demonstrate that the TM ions in O3 NaMnO 2 , NaFeO 2 and NaCoO 2 adopt a high spin state. Structurally, NaMnO 2 and NaPdO 2 undergo Jahn-Teller distortions while NaNbO 2 undergoes puckering distortion. Furthermore, in addition to Jahn-Teller distortion, NaPdO 2 exhibits charge disproportionation as it contains Pd 2+ , Pd 3+ and Pd 4+ species. These distortions stabilize the inter-plane ferromagnetism. Additionally, the inter-plane ferromagnetic coupling is stabilized by kinetic p-d exchange mechanism in undistorted NaCoO 2 , NaNiO 2 and NaTcO 2 . The intra-plane coupling in this family of compounds on the other hand was found to be generally weak. Only NaMnO 2 , NaNiO 2 and NaTcO 2 are predicted to show bulk ferromagnetism with estimated Curie temperatures below ∼50 K.