Inducing Spin Canting by Octahedral Rotations in Antiferromagnetic Perovskites

It is well known that lattice distortions in magnetic perovskite oxides can be used to modify the exchange interactions and the Dzyaloshinsky-Moriya interaction (DMI)¹. In principle, it is possible to modulate these lattice distortions, such as octahedral rotations and A-site atomic displacements and, in turn, alter the associated properties by using techniques such as doping, straining, or external fields. Unfortunately, the actuation with electric fields is usually weak due to the lack of space-inversion symmetry breaking by these rotations.<br/>Recently we proposed a strategy that exploits point defects that create local electric dipoles and couple to the oxygen sublattice, enabling direct actuation on the rotational degrees of freedom². By extending this approach, we rationalize the connection between lattice distortions, spin order and spin canting in antiferromagnetic (AFM) perovskites. Using DFT calculations³ we validate a set of simple rules that can be used to identify which structural distortions can be tuned to induce spin canting (and weak ferromagnetism) in antiferromagnetic systems. We apply these rules to study Al-doped LaFeO₃ and strained CaMnO₃ perovskites, discussing effects on spin canting and AFM order.<br/>Bibliography:<br/>1. C. Weingart, N. Spaldin, and E. Bousquet. “Noncollinear magnetism and single-ion anisotropy in multiferroic perovskites”. Phys. Rev. B 86, 09441 (2012).<br/>2. J Jia, X He, A Akhtar, G Herranz, and M Pruneda ”Dynamic control of octahedral rotation in perovskites by defect engineering” Phys. Rev. B 105, 224112 (2022).<br/>3. J. M. Soler, et al, “The SIESTA method for ab-initio order-N materials simulation”, J. Phys.: Condens. Matt. 14, 2745 (2002).