Microscopic origin of altermagnetism through the lens of chemical bonding

In recent years, altermagnets have drawn significant attention due to their various unconventional properties. Particularly, the symmetry driven spin split of the bands in the momentum space with compensated magnetism opens a new avenue to study various properties of an antiferromagnet in the presence of broken time reversal symmetry. While a lot of research is being carried out in designing the futuristic quantum devices using altermagnet, the fundamental understanding of the origin of altermagnetism is still evolving. The existing group theory can only provide a binary description of the existence of altermagnetism, but not any quantitative description. The latter is crucial for device application. Therefore, we have studied the origin of altermagnetism in the framework of chemical bonding that provides a quantitative description of altermagnetic spin-splitting and is tunable. Most importantly, we identified the deterministic chemical bonding that drives the altermagnetism. Furthermore, we propose a new class of magnetism called "quasi-altermagnetism" and explain its chemical bonding origin. This study prepares a fertile ground to develop chemical bonding driven selection rules for the classification of different types of magnetism.