Robust antiferromagnetism in NaOsO₃ under pressure

NaOsO₃ is known to be an insulator with a small band gap of 0.2 eV, favoring a G-type antiferromagnetic state below 410 K. It is believed to be an example of a Slater insulator [1], with spin-orbit interactions playing a significant role here in modifying the electronic structure[2]. The unusually high antiferromagnetic temperature has been explained as emerging from the half-filling of the t_2g  state [3]. We have examined the pressure dependence of the electronic structure, as well its evolution under pressure both in the presence and absence of spin-orbit interactions within ab-initio electronic structure calculations. Mapping the Hamiltonian to a tight-binding model, we use pressure as a parameter to tune the interaction strengths and bring it to the point where magnetic order just sets in. This allows us to throw light on the mechanism of magnetism.

[1] J. C. Slater, Phys. Rev. 82, 538 (1951)

[2] R. Sereika, P. Liu, B. Kim et al., npj Quantum Mater. 5, 66 (2020)

[3] S. Middey, S. Debnath, Priya Mahadevan and D.D. Sarma, Phys. Rev. B, 89, 134416 (2014)