Helical magnetism in Weyl materials

The magnetic structures and excitations of topological magnetic semi-metals are of great fundamental interest and key to understanding the unique transport properties of these materials. I will provide an overview of recent neutron and synchrotron x-ray scattering experiments exploring the magnetism of Weyl materials based on transition metals and rare earth elements. I will contrast the commensurate and incommensurate magnetic structures of Mn3Ge and MnSn and relate them to the magnetic excitations and interactions [1,2]. For the rare earth case, I will describe the intricate helical magnetism of NdAlSi and its connection with the underlying electronic band structure [3]. The talk will illustrate the power of novel scattering instrumentation and the importance of combining information from multiple experimental techniques and with theory for a comprehensive understanding of the interplay between charge and spin in topological semi-metals.