Post-doctoral position - ODE Beamline

Located on the Paris-Saclay plateau, about 20 kilometers from the capital, the SOLEIL synchrotron is one of France's leading research facilities. Since it began operating in 2008, it has served the national and international scientific communities. Research conducted at SOLEIL covers a wide range of scientific and industrial fields — including physics, biology, chemistry, materials science, environmental science, Earth sciences, and cultural and natural heritage — all connected to current societal challenges. Experiments carried out on the beamlines rely on the use of synchrotron light emitted by electrons accelerated to nearly the speed of light within a storage ring. SOLEIL is jointly supervised by the CNRS and the CEA and offers its staff a dynamic, innovative, multidisciplinary, and international working environment.

At the forefront of technology, SOLEIL II is an ambitious project designed to provide new opportunities for scientific and industrial research. SOLEIL II consists of a major upgrade of the existing infrastructure and aims to significantly improve the performance of electron accelerators and beamlines. It is designed to address major current and future societal challenges, particularly in areas such as advanced materials research, energy and sustainable development, health and well-being, and the environment.

Construction work on the SOLEIL II project began in 2024, marking the start of a phase of development and technological innovation. In parallel, the existing facility will remain operational until the fall of 2028. SOLEIL II is scheduled to start operations in 2030, with a gradual ramp-up phase continuing until 2035.

The ODE (Optique Dispersive EXAFS) beamline is dedicated to x-ray absorption spectroscopy in the hard x-rays range (5-25 keV), using an energy dispersive set-up. XANES, XAFS and XMCD (using a magnetic field) measurements are currently performed.

For further details: https://www.synchrotron-soleil.fr/fr/lignes-de-lumiere/ode

Context and missions

Under the supervision of Lucie Nataf and in collaboration with Anne Bleuzen and Amélie Bordage from ICMMO (Université Paris Saclay), the post-doctoral fellow will participate in the beamline's missions:

- the post-doctoral fellow will have to develop a research topic exploiting the experimental possibilities of the ODE beamline, with the aim to go deeper in the understanding of XMCD signals in the hard X-rays range, and demonstrating to the scientific community in molecular magnetism the interest of this technique for their research.;

- he.she will accompany the beamline scientists to assist the external user teams (setting of the beamline, installation of the sample environment, support to the users during their experiment time) ;

- he.she will participate to the experimental development, with the commissioning of the 7 Teslas magnet and the new cryostat associated with it.

- he.she will participate in scientific conferences related to the research developed and/or the experimental and technical possibilities of the beamline. He/she will also write his/her results in scientific journal articles.

Recently, the versatile chemistry of bimetallic Prussian Blue Analogues (PBAs), and the description of their electronic structure using a 'molecular orbital' approach, have been used to better understand XMCD signals in the hard X-ray range^1,3. This study has made it possible for the first time to relate XMCD signal characteristics to the electronic structure and local magnetism of transition metal ions in these molecular systems and to establish expressions that accurately reproduce the signal intensities. These advances now make it possible to use transition metal K-edge XMCD to probe locally the magnetism of ABPs. They have also suggested a relationship between the orientation of the magnetic moment relative to the crystallographic structure and the intensity of the XMCD signal. The use of XMCD to understand the local magnetic properties of ABPs on the one hand, and the use of rare-earth and transition metal coordination compounds to better understand the role of magnetic moment orientation on XMCD signals on the other, are at the heart of the two proposed axes of research.

1) Use of K-edge XMCD on transition metal to understand the local magnetic properties of ABPs 

Trimetallic ABPs are more complex than bimetallic ABPs, both in terms of the interpretation of XMCD signals and in terms of the properties exhibited by these compounds. These trimetallic compounds of chemical formulae (A_xA'_1-x)₄[B(CN)₆]_3/8 and A₄[(B_xB'_1-x)(CN)₆]_3/8 display original magnetic properties due to the competition between the exchange interactions of the two sublattices (A and B). A first study showing the novel contribution of XMCD at transition metal K-edge to understanding the properties of CoNiFe ((Co_xNi(_1-x))₄[Fe(CN)₆]_3/8⁴ series compounds opens up a new field of research to be explored, the number of possible transition metal combinations in these systems being infinite.

Some bimetallic and trimetallic ABPs also exhibit photo-induced switching properties. The study of local magnetic properties in such photo-induced states, almost unexplored, represents another open field of research.

2) Use of rare-earth and transition metal coordination compounds to better understand the role of magnetic   moment orientation on XMCD signals

Another focus will be on single crystals of rare-earth mono and polymetallic molecular complexes and single crystals of cyanide-bridged transition metal chains, in collaboration with the Laboratoire de Chimie de Coordination in Toulouse. Most of these systems exhibit a magnetic anisotropy whose orientation is known with respect to the crystallographic axes. XMCD measurements of these systems require the application of a magnetic field able to reach 7T and the orientation of single crystals.

The post-doctoral fellow will be encouraged to use other experimental techniques, either at SOLEIL (on other light lines such as AILES, PSICHE, CRISTAL, GALAXIES...) or outside the synchrotron, in particular in collaboration with nearby laboratories of Paris-Saclay.

[1] A. N’Diaye et al., J. Synchrotron Rad., 28, 1127, 2021 ; [2] A. N’Diaye et al., Inorg. Chem., 61, 6326, 2022; [3] A. N’Diaye et al., ACS Omega, 7, 41, 36366, 2022; [4] A. N’Diaye et al., Phys. Chem. Chem. Phys., 26, 15576, 2024.

Profile

The candidate should have a PhD degree, or equivalent qualification, in condensed matter physics, materials physics or chemistry, or in a related discipline.

The candidate should have strong experimental skills, including data processing.

He/she should be autonomous and take full responsibility for the experiments, in particular those performed on the ODE line (including beam time requests).

The following aspects will be considered with particular attention :

• Experience in x-ray absorption spectroscopy (EXAFS, XANES, XMCD) with a particular emphasis on the XMCD technique ;
• Ability to conduct research ;
• Ability and taste for teamwork.

The candidate must be fluent in English.

Benefits :

• 26 days of paid vacation + up to 2 extra days + 23 RTT days per full working year, based on a 40-hour workweek.
• Mandatory health insurance (basic plan) costs 19.35 euros per month for the employee (174.15 euros cost for the employer, covering 90% of the contribution), including family members (spouse + children).
• We offer optional supplementary health insurance for your family (partner + children) at 26,69 euros.
• Benefit from a welfare system that supplements mandatory Social Security benefits, often insufficient. It compensates for lost income in case of inability to work, ensuring the standard of living for the insured and their family in difficult circumstances: death, incapacity to work, or disability due to illness or accident.
• Possibility to open a Time Savings Account (CET) after one year of seniority: The CET allows you to accumulate earned rest days in view of compensating for leave, buying back retirement insurance quarters, funding an enterprise savings plan (PEE) and/or a collective retirement savings plan (PERCO), and monetizing acquired days. Employer’s complementary contribution to the retirement savings plan (PERCO).
• On-site company restaurant at SOLEIL, with subsidized meals (cost for the employee ranges from approximately 3.30 euros to 6.75 euros, depending on salary scale).
• Family benefits according to different situations: family bonus, additional leave in certain situations, wedding, and birth bonuses...
• Social and cultural activities offered by SOLEIL's Social and Economic Committee (CSE).