Using ab initio wave-function-based calculations, we provide valuable insights with regard to the magnetic exchange in 5d and 4d oxides with face-sharing ligand octahedra, BaIrO3 and BaRhO3. Surprisingly strong antiferromagnetic Heisenberg interactions as large as 400 meV are computed for idealized iridate structures with 90∘ Ir-O-Ir bond angles and in the range of 125 meV for angles of 80∘ as measured experimentally in BaIrO3. These estimates exceed the values derived so far for corner-sharing and edge-sharing systems and motivate more detailed experimental investigations of quantum magnets with extended 5d/4d orbitals and networks of face-sharing ligand cages. The strong electron-lattice couplings evidenced by our calculations suggest rich phase diagrams as function of strain and pressure, a research direction with much potential for materials of this type.
@article{arxiv.1902.07269,
title = {Superexchange interactions between spin-orbit-coupled $j\!\approx\!1/2$ ions in oxides with face-sharing ligand octahedra},
author = {Lei Xu and Ravi Yadav and Viktor Yushankhai and Liudmila Siurakshina and Jeroen van den Brink and Liviu Hozoi},
journal= {arXiv preprint arXiv:1902.07269},
year = {2019}
}