Magnetic X-ray absorption spectroscopy

The basic principles of the magnetization dependent effects of the absorption of circularly polarized X-rays are discussed. At the inner core absorption edges, the effect is manifested in a difference of absorption coefficients for the right and left circularly polarized quanta in ferromagnetic media and is called X-ray magnetic circular dichroism (XMCD). It originates from the interplay of spin orbit interaction in the initial state and angular momentum conservation in the absorption process and reflects the local spin and orbital polarization of the final states. An outstanding feature of XMCD is the applicability of the so-called sum rules which can be used to determine spin and orbital contributions to the local magnetic moments separately.