The non-resonant magnetic X-ray scattering cross-section for photon energies up to 500 keV

– Results of high-energy magnetic X-ray diffraction for photon energies up to 500 keV are presented and the form of the magnetic scattering cross-section for relativistic energies is discussed. At 300 keV we experimentally proved that the scattering from the spin component perpendicular to the scattering plane is dominant. Within our statistical and systematic errors, the magnetic scattering amplitude for this component does not exhibit any variation with energy between 100 and 500 keV. Introduction. – Magnetic X-ray diffraction with high-energy photons exhibits certain advantages with respect to neutron and medium-energy X-ray diffraction which are discussed in detail in [1], [2]. These include true bulk sensitivity, volume-enhancement of the magnetic signal, high momentum space resolution and a simple form of the magnetic scattering crosssection. For this reason, magnetic scattering with hard X-rays at an energy of 80 keV has been developed during the last years [1], [2]. At this energy, the first-order approximation in h̄ω/mc for the magnetic scattering amplitude is valid in very good approximation. For magnetic diffraction at higher energies, when the photon energy approaches the electron rest mass mc = 511 keV, a complete quantum-relativistic treatment is necessary, taking into account all effects arising from the coupling of the quantized photon field and the Dirac field of the electrons. To our knowledge, a corresponding theory is missing. To investigate experimentally how the scattering cross-section behaves for higher photon energies, we measured magnetic Bragg reflections of MnF2 at energies up to 500 keV. Magnetic scattering cross-section for hard X-rays. – A calculation of the cross-section for X-ray scattering including the magnetic terms from a quasi-relativistic Hamiltonian for () Present address: Forschungszentrum Jülich, Institut für Streumethoden, D-52425 Jülich, Germany. c © Les Editions de Physique 570 EUROPHYSICS LETTERS