Extremely strong spin−orbit coupling effect in light-element altermagnetic materials

Spin−orbit coupling is a key to realize many novel physical effects in condensed matter physics. Altermagnetic materials possess the duality of real-space antiferromagnetism and reciprocal-space ferromagnetism. It has not been explored that achieving strong spin−orbit coupling effect in light-element altermagnetic materials. In this work, based on symmetry analysis, the first-principles electronic structure calculations plus dynamical mean-field theory, we demonstrate that there is strong spin−orbit coupling effect in light-element altermagnetic materials NiF3 and FeCO3, and then propose a mechanism for realizing such effective spin−orbit coupling. This mechanism reveals the cooperative effect of crystal symmetry, electron occupation, electronegativity, electron correlation, and intrinsic spin−orbit coupling. Our work provides an approach for searching light-element altermagnetic materials with an effective strong spin−orbit coupling.