Physical property analysis of antiferromagnets based on cluster multipole method and electronic structure calculation

This paper explains the principles of the cluster multipole method, which describes the magnetic structure through multipole expansion, and introduces the studies that apply them. First, it discusses the space groups that characterize the symmetry of crystals and magnetic structures as well as the relationship between the structure of the magnetic space group and physical properties, and summarizes the relationship between symmetry and physical property phenomena. In addition, it proposes a method to summarize the formulas for multipole expansion for continuous magnetization distributions and to augment the formulas to magnetic arrays on atomic clusters, and discusses the problems in augmenting this method to magnetic structures in crystals. It explains a method for corresponding the magnetic structure of a crystal to multipole moment, as well as a formula for multipole expansion for a general magnetic structure. It introduces research examples on the electronic state, magnetic properties, and transport phenomena in Mn₃Sn and Mn₃AN (A: transition metals) based on the combined use of first-principles calculations. (A.O.)