F. de Bergevin

Femtoscale Magnetically Induced Lattice Distortions in Multiferroic TbMnO3

Ferroelectric order in a multiferroic compound is probably caused by small displacements of ions in its crystal lattice. Magneto-electric multiferroics exemplified by TbMnO3 possess both magnetic and ferroelectric long-range order. The magnetic order is mostly understood, whereas the nature of the ferroelectricity has remained more elusive. Competing models proposed to explain the ferroelectricity are associated respectively with charge transfer and ionic displacements. Exploiting the magneto-electric coupling, we used an electric field to produce a single magnetic domain state, and a magnetic field to induce ionic displacements. Under these conditions, interference between charge and magnetic x-ray scattering arose, encoding the amplitude and phase of the displacements. When combined with a theoretical analysis, our data allow us to resolve the ionic displacements at the femtoscale, and show that such displacements make a substantial contribution to the zero-field ferroelectric moment.

ID20: a beamline for magnetic and resonant X-ray scattering investigations under extreme conditions.

A new experimental station at ESRF beamline ID20 is presented which allows magnetic and resonant X-ray scattering experiments in the energy range 3-25 keV to be performed under extreme conditions. High magnetic field up to 10 T, high pressure up to 30 kbar combined with low temperatures down to 1.5 K are available and experiments can be performed at the M-edges of actinide elements, L-edges of lanthanides and K-edges of transition metals.

X‐ray polarimetry with phase plates

Diamond crystals were used as quarter‐wave plates (QWPs) and half‐wave plates (HWPs) to produce and completely analyze circular and vertical linear polarization of monochromatic x rays from an undulator source (ID10) at the European Synchrotron Radiation Facility. The horizontal linear polarization state of the forward diffracted beam in the Bragg or Laue geometry was efficiently converted into circular (99%) and vertical polarization (97%) by tuning the crystal conveniently away from the Bragg peak. Also, the combination of two QWPs was used to obtain linear polarization at any desired azimuth (e.g., 95% at 45°). Further, the second QWP and the linear polarimeter were used to completely characterize the polarization state of the circularly polarized beam after the first QWP. High efficiencies at QWPs and HWPs and high transmitted intensity (40%) were achieved with the diamond crystal in the asymmetric Laue geometry.

Perfect crystal and mosaic crystal quarter‐wave plates for circular magnetic x‐ray dichroism experiments

Circular magnetic x‐ray dichroism experiments require circularly polarized x rays usually provided by bending magnet synchrotron radiation below or above the orbit plane. It is shown here that a very promising alternative consists of using linearly polarized x rays converted to circularly polarized ones by quarter‐wave plates made of nonabsorbing crystals like good diamond crystals and also mosaic beryllium crystals. Convincing experimental results obtained on the energy‐dispersive absorption spectrometer at LURE (Orsay‐France) are presented.

Experimental evidence of anapolar moments in the antiferromagnetic insulating phase of V 2 O 3 obtained from x-ray resonant Bragg diffraction

We have investigated the antiferromagnetic insulating phase of the Mott-Hubbard insulator vanadium sesquioxide

Interplay between orbital and magnetic long range order by resonant X-ray scattering in (V1−xCrx)2O3☆

({\text{V}}_{2}{\text{O}}_{3})

The Interaction of X-Rays (and Neutrons) with Matter

by resonant x-ray Bragg diffraction at the vanadium

Resonant Surface Magnetic X-Ray Diffraction from Co3Pt(111).

K

Electric field control of multiferroic domains in Ni 3 V 2 O 8 imaged by x-ray polarization-enhanced topography

edge. Combining the information obtained from azimuthal angle scans, linear incoming polarization scans and by fitting collected data to the scattering amplitude derived from the established chemical

Magnetic structure of Sm_ {2} IrIn_ {8} determined by x-ray resonant magnetic scattering

I2/a