On December 2th at 11:00, we have the pleasure to welcome Nicolas Jaouen from SEXTANTS beamline, Synchrotron SOLEIL. He will give us a seminar at CEA/SPINTEC (*) Bat 1005, room 445, entitled :

Chirality in thin films and multilayers probed by Soft x-ray (coherent) scattering

Many current forthcoming applications of magnetic materials involve heterostructures or alloys containing magnetic and non-magnetic elements. X-ray Resonant (Coherent) Scattering is the technique of choice to probe such phenomena thanks to its element-selectivity and spatial sensitivity.
In this presentation I will introduce the experimental set-up that we developed at SOLEIL and illustrate their capabilities. SEXTANTS [1] is a beamline of the SOLEIL synchrotron, covering the 50-1700eV energy range dedicated to soft x-ray scattering. The resolving power exceeds 1e4 and maximum flux on the sample ranges from 1e14 (100 eV) to 2e13 (1000 eV) ph./s/0.1% bw. The beamline main objective is the investigation of the electronic and magnetic properties of solids using three scattering techniques: resonant inelastic x-ray scattering (RIXS), x-ray resonant magnetic scattering (XRMS) and coherent x-ray scattering (CXS), the last one including also imaging via Fourier transform holography (FTH) [2, 3].
In the second part, several recent results obtained at SEXTANTS beamline will be presented, and in particular I will show that XRMS is the tool to study magnetic chirality as illustrated with two systems: on one hand, I will briefly introduce the approach using prototype Pt/Co multilayers in which Dzyaloshinskii-Morya interaction (DMI) is induced by the inversion symmetry breaking at the interfaces [3,4] and on the other hand, an investigation we have done of BiFeO3 thin epitaxial layers in which the “bulk” DMI plays a major role in its magnetic configuration and in particular in the stabilization of the antiferromagnetic cycloid. Combining real space [5] and reciprocal space [6] approach we reveal the presence of periodic chiral AFM objects along the ferroelectric (FE) domain walls.
In the last part I will present the latest development of resonant scattering and in particular how the use of the x-ray coherence already available at modern light source, and expected to increase by few order of magnitude in the planned upgrade sources, allow nowadays to image the sample with a spatial resolution of few tens of nanometers and a time resolution ranging from ns down to few ps timescale.
[1] M. Sacchi et al., Journal of Physics: Conference Series 425 (2013) 072018
[2] S. Eisebitt et al., Nature, 432, 885 (2004).
[3] H. Popescu et al. J. Synchr. Rad 26, 280 (2019)
[3] J.Y. Chauleau et al. Phys. Rev. Lett. 120, 037202 (2018).
[4] W. Legrand et al. Sci. Adv. 2018, 0415 (2018).
[5] I. Gross et al., Nature 549, 252 (2017).
[6] J.Y. Chauleau et al Nat. Materials, to appear.

Biography : After his PHD at the CNRS Grenoble (2001), he was postdoc and staff scientist at ESRF then SOLEIL and principal Beamline Scientist for the construction of sextants Beamline at SOLEIL(2007-2008). Since he is principal beamline scientist, Synchrotron SOLEIL, in charge of the SEXTANTS team, composed of two beamline scientists, one assistant engineer and, on average, two Ph.D. students and one post-doc.
He is an experimental physicist who utilizes synchrotron radiation based techniques for the investigation of the electronic structure of matter, its magnetic properties and structural phenomena. His current research addresses charge and spin order phenomena and their dynamics occurring in nano‐structured materials, thin films and at their surfaces by resonant scattering of x-rays, including magnetic scattering, coherent scattering as well as inelastic scattering.

1.  Chauleau, J.Y. et al. A Physical Review Letters., 120, 037202 (2018)
2. Gross, I. at al. Nature. 549(7671): 252–256 (2017)
3. Jal E et al. Phy. Rev. B 95, 184422 (2017)
4. Gibert et al. Nat. Comm. 7, 11227 (2016)
5. J.Y. Chauleau et al. Nat. Materials, to appear.

(*) Persons who do not have a CEA badge must request an entry authorization sufficiently in advance, before November 21th at sabrina.megias@cea.fr or celine.conche@cea.fr