Ab Initio Approaches for Low-Energy Spin Hamiltonians

Implicit in the study of magnetic materials is the concept of spin Hamiltonians, which emerge as the low-energy theories of correlation-driven insulators. In order to predict and establish such Hamiltonians for real materials, a variety of first principles ab initio methods have been developed, based on density functional theory and wavefunction methodologies. In this Feature Article, a basic introduction to such methods and the essential concepts of low-energy Hamiltonians is provided, with a focus on their practical capabilities and limitations. Furthermore, recent efforts toward understanding a variety of complex magnetic systems that present unique challenges from the perspective of ab initio approaches are discussed.