Probing magnetic excitations in correlated electron materials using inelastic neutron and X-ray scattering

In correlated electron systems, magnetic interactions in various forms can yield rich exotic magnetic ground states including antiferromagnetic Mott insulator, antiferromagnetic Hund's metal, quantum spin liquid, low-dimensional quantum magnets, and topological magnets. To understand the microscopic mechanism and underlying physics of these materials, it is essential to probe the magnetic excitations and obtain detailed information about the spin-spin interactions by modeling the dynamical structure factor of the spin excitations. Although several techniques have been developed to measure the spin dynamics of magnetic systems, inelastic neutron scattering (INS) and resonant inelastic X-ray scattering (RIXS) have proven to be powerful and complementary probes in mapping the elementary magnetic excitations over a wide energy and momentum range. Furthermore, INS is a well-established technique requiring a large sample volume, whereas RIXS is a fast-developing method that can measure small crystals, including thin films and heterostructure samples, with high efficiency. This review focuses on discussing the comparison and combination of INS and RIXS in measuring the magnetic excitations of several prototypical correlated electron materials, demonstrating that combining INS and RIXS enables us to study the magnetic excitations in almost all magnetic correlated electron systems, including low-dimensional materials.