X-ray Absorption Magnetic Circular Dichroism (XMCD)

X‐ray absorption magnetic circular dichroism (XMCD), which utilizes synchrotron radiation, has become one of the most powerful tools to investigate microscopic information on the magnetic properties of ferromagnetic materials. In a ferromagnetic system, the X‐ray absorption rate becomes different for different photon helicity vectors, right and left circular polarized light, and the difference in the absorption rate provides information on the spin and the orbital magnetic moments separately. The orbital magnetic moment is mostly quenched in solids and is often neglected. However, because the magnetic anisotropy is determined by this small orbital magnetic moment through the spin‐orbit coupling, it plays a critical role in the magnetic behavior. Further, the core level absorption energy is characterized by the element; thus, XMCD is a unique way to determine the element-specific spin and orbital magnetic moments. This article presents a brief introduction to X‐ray absorption spectroscopy and X‐ray magnetic circular dichroism experimental techniques.