Orbital Contributions to Magnetism in Noncollinear Antiferromagnets
Hua Chen, Colorado State University
February 12, 2021
Although usually overshadowed by their spin counterparts, orbital contributions to magnetization of condensed matter systems are fundamentally interesting and appear to be especially relevant in antiferromagnets where the net spin moment is strongly suppressed. In the first part of the talk I will discuss the role of orbital magnetic moment in the coupling between the order parameters of certain noncollinear antiferromagnets having the anomalous Hall effect and magnetic fields. We find that the orbital moments tend to dominate over spin moments, especially so when spin-orbit interactions are weak. We explain how magnetic fields can be used to manipulate magnetic configurations indirectly through their coupling with the orbital moments in these systems. In the second part of the talk I will discuss how to understand the local density of orbital magnetization in the context of magnetic neutron scattering. We show that magnetic neutron scattering in general maps out the equilibrium electric current distribution inside the material but leaves the magnetization density unfixed because of a gauge freedom. We discuss the connection between the equilibrium current density and the modern theory of orbital magnetization, and provide examples on calculating the orbital contribution to elastic neutron cross-section using models and first-principles methods.