16 November 1999 Ferromagnetism studied with circularly polarized x rays
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In practice x-ray studies of ferromagnetic materials require circularly polarized radiation if the weak momentum-dependent signal is to be separated from the dominant charge scattering in either elastic (diffraction) experiments or inelastic (Compton scattering) studies. In both methods it is necessary to modulate the photon's helicity or the sample's magnetization. The former method is the more desirable because it is effective in magnetically hard materials, but it is more difficult to achieve than the latter. To date inelastic Compton scattering, which is solely sensitive to the spin moment, is the better developed technique. It has benefited from the availability of high fluxes of high energy x-rays (60 - 300 keV) at third generation synchrotron sources. This has led to an improvement of a factor of two in resolution, but further improvements are flux limited. In the 3d elemental and compound ferromagnets the method has been used to establish the validity not only of the electronic structure calculation but also the underlying approximations. In compound ferromagnets it has been used to determine site-dependent spin moments. Examples will be given from recent studies of alloys and other rare earth compounds. The development of similar techniques using circularly polarized beams to diffraction studies of spin and orbital magnetization will also be described.
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Malcolm J. Cooper, Malcolm J. Cooper, Jonathan A. Duffy, Jonathan A. Duffy, "Ferromagnetism studied with circularly polarized x rays", Proc. SPIE 3773, X-Ray Optics Design, Performance, and Applications, (16 November 1999); doi: 10.1117/12.370101; https://doi.org/10.1117/12.370101

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