Magnetic scattering of x rays (invited)

The scattering of x rays is used to determine the electric charge distribution in matter. Since x rays are electromagnetic radiation, we should expect that they will be sensitive not only to the charge distribution, but also to the magnetization density. That this is indeed the case has been pointed out and studied experimentally. In this paper the magnetic scattering is discussed in a way which allows consideration of the effects of electron binding. The cross section, compared with that for neutron scattering from magnetically ordered materials, is reduced by (ℏω/mc2)2 (about 5×10−4). With a synchrotron radiation source, however, this factor can be made up, and magnetic x-ray Bragg peaks can be collected in the same time as neutron peaks. Special effects of interest include high momentum resolution, polarization phenomena which separate spin and orbital densities, and resonance effects which give a large enhancement of the x-ray cross section and which may make the study of surface magnetism possible.