PhD Student on ID12 in the Electronic Structure, Magnetism & Dynamics

Thesis subject: New functional materials obtained by hydrogen insertion in intermetallic magnets

Magnets based on 3d transition metals (such as Fe and Co) have been studied for decades due to their rich variety of magnetic properties, offering an excellent platform to explore the fundamentals of solid state magnetism. These compounds also play a vital role in modern technologies, serving as permanent magnets in the electromotive industry and wind turbines, or as magnetocaloric materials for environmentally friendly refrigeration systems. Interestingly, some of these systems can store hydrogen into their crystal lattice, making them promising candidates for green energy applications. Hydrogen insertion leads to a significant expansion of the lattice and, in some cases, changes in crystal symmetry. These structural modifications strongly impact the magnetic properties, such as increasing the ordering temperature and coercivity, or even transforming an antiferromagnet into a ferromagnet. Remarkably, certain alloys become superconducting when hydrogen is introduced.

The main objective of this PhD thesis is to unravel the microscopic mechanisms by which the hydrogen affects the properties of these materials. To achieve this goal, we will make full use of X‐ray Absorption Spectroscopy (XAS), including X‐ray Magnetic Circular Dichroism (XMCD) - an inherently element- and orbital-selective technique - alongside X‐ray diffraction (XRD) and macroscopic magnetic measurements. To separate the effects of “chemical” pressure from those of lattice expansion, XAS will also be conducted under applied external pressure. Additionally, high-pressure hydrogen synthesis will be explored to extend the accessible range of hydrogen content. The key expected outcome of this work is a deeper understanding of the role of hydrogen in the complex interplay between lattice, electronic and magnetic degrees of freedom, knowledge that is essential for future technological applications.

The project will be carried out jointly at Néel Institute (Grenoble, France) and at the ESRF ID12 beamline (Grenoble, France), under the co-supervision of Dr. Fabrice Wilhelm (ESRF) and Prof. Olivier Isnard (Néel Institute).

This PhD project is co-funded within the framework of the GATES project, enabling the partners to combine their complementary expertise to deliver pioneering, high-impact research on these novel functional materials.

Further information can be obtained from Dr. Fabrice Wilhelm (tel.: +33 (0)4 76 88 24 19, email: wilhelm@esrf.fr) and Prof. Olivier Isnard (tel.: +33 (0)4 76 88 11 46, olivier.isnard@neel.cnrs.fr)