A high Neel temperature 5$d$ oxide: NaOsO${}_3$

Abstract

The origin of a high Neel temperature in a 5$d$ oxide, NaOsO${}_3$, has been analyzed within the mean-field limit of a multiband Hubbard model and compared with the analogous 4$d$ oxide, SrTcO${}_3$. Our analysis shows that there are a lot of similarities in both these oxides on the dependence of the the effective exchange interaction strength ($J_0$) on the electron-electron interaction strength ($U$). However, the relevant value of $U$ in each system puts them in different portions of the parameter space. Although the Neel temperature for NaOsO${}_3$ is less than that for SrTcO${}_3$, our results suggest that there could be examples among other 5$d$ oxides which have a higher Neel temperature. We have also examined the stability of the G-type antiferromagnetic state found in NaOsO${}_3$ as a function of electron doping within GGA+U calculations and find a robust G-type antiferromagnetic metallic state stabilized. The most surprising aspect of the doped results is the rigid band-like evolution of the electronic structure which indicates that the magnetism in NaOsO${}_3$ is not driven by fermi surface nesting.

Accepted in Phys. Rev. B (Regular article)