ID20 - Magnetic Scattering Beamline

ID20 Home Page
ID20 Users Guide
ID20 Technical Information

Contact	Tel: +33 (0)4 76 88 +ext
Luigi PAOLASINI, Scientist in charge	24 02
Carsten DETLEFS, Scientist	25 56
Flora YAKHOU, Beamline operation manager	24 91
ID20 Control Room	26 43

Synopsis

The beamline ID20 is optimized for the study of electronic and magnetic properties of solids, in particular magnetic, charge and orbital ordering. The versatility of this beamline makes it unique in the conception and implementation of new ideas for experiments. The very recent developments in coherent magnetic scattering, orbital ordering and magnetic surface experiments by the scientists of this beamline are just a few examples. A new experimental hutch with a second diffractometer designed to support a 10T superconducting split-coil cryomagnet will be available for user experiments in 2004.

The beamline is designed to achieve the following:

• a large tunable energy-range i.e. 3 keV < E < 30 keV;

• a very good energy resolution (i.e. E/E < 10^-4) to scan an element's absorption edge;

• a high rate of harmonic rejection (<10^-4) due to the use of two mirrors;

• linear polarization analysis of scattered photons;

• complex sample environments (low temperatures, pressure, high magnetic fields).

Scientific Applications

X-ray magnetic scattering complement the magnetic neutron scattering technique regarding sample size, Q-resolution, single magnetic domain studies, separation of angular and spin contributions to the magnetic moment, and magnetic ordering of non-suitable, highly neutron absorbing, compounds. Moreover, the site and shell selectivity of x-ray resonant scattering allow for the exploration of the anisotropic properties of atomic scattering tensors, and thus represent an unique method to characterize magnetic interactions from electronic point of view.

Techniques Available

Polarization analysis

The state of linear polarization of the scattered beam may be determined by the use of an analyzer crystal with scattering angle of approximately 90$^\circ$. A large set of such crystals, covering a wide energy range, is available. Furthermore, the polarization of the incident beam may be modified with an x-ray phase plate.

Non Resonant magnetic x-ray scattering (NRMXS)

Quantitative information on the orbital magnetic moment can be obtained by the linear polarization analysis of scattered photons. By tuning the incident photon energy far from any absorption edge, and measuring the ratio of scattered polarization state on a magnetic Bragg satellite, either parallel ($\pi$) or perpendicular ($\sigma$) to the scattering plane, it is possible to extract information on ratio of orbital and spin magnetic moment, L/S.

Resonant x-ray scattering (RXS)

Large resonant enhancements of the scattering cross section may be observed when the incident photon energy is tuned close to an atomic absorption edge, e.g., the M_4,5 edges of actinides, the L_2,3 edges of rare earths, or the K edges of transition metals. Resonances sensitive to magnetic and quadrupolar order have been observed. The resonant cross section has a characteristic polarization dependence, which may be exploited to obtain further information on the magnetic moment direction and the space group of the ordered state. The technique is particularly powerful when polarization analysis of the scattered beam is used in combination with azimuthal scans, where the sample is rotated about the scattering vector.

Complementary Information

ID20 Home Page
ID20 Users Guide
ID20 Technical Information
Location in the storage ring and plan of the beamline (pdf)
Specifications (pdf)

Keywords:

single crystal diffraction, magnetic scattering, antiferromagnetism, orbital order, quadrupolar order, polarized x-rays, coherent x-ray diffraction.