INTERNSHIPS 2025:

• Master 1 level (April 2025): Numerical study of magnetic relaxation in ferromagnetic thin films by ferromagnetic resonance

• Master 2 level (March 2025): Study of memory and aging properties in nanomagnets : spin-glass behavior versus superparamagnetism

PHD 2025:

• Study of magnetic alloys for enhanced functionality

The scientific project proposes the study of static and dynamic magnetic properties of thin layers or composite structures (nanoparticles, nanofibers) of multifunctional materials such as Heusler alloys or composite multiferroics.In particular, the synthesis of high quality magnetic films is envisaged and the use of SQUID magnetometry and ferromagnetic resonance (FMR) spectroscopy for theirs characterization. The potential candidate must have a solid background in condensed matter physics. His/her activities will cover the synthesis of thin films, magnetic characterization as well as experimental development of FMR setup. Knowledge directly related to the project (nanomagnetism, spintronics, spin dynamics) will be appreciated. Keywords : Multifunctional Materials, Spintronics, Ferromagnetic Resonance

Main research themes:

• Study of formation, propagation and interaction of magnetic textures in nanostructures: spin waves, domain walls (transverse, vortex, antivortex)

• Magnetic relaxation and magnetic dissipation: intrinsic and extrinsic mechanisms of magnetic damping

• Multifunctional materials: study of different couplings (magneto-structural, magneto-caloric, magneto-électric) in thin films or nanostructures (nanoparticles, nanofibers) of intermetallic alloys, manganites, multiferoics

Recent Research:

Multifunctional materials:

- Interplay between magnetisation dynamics and structure in MnCoGe thin films (link article): Rrelation between magnetisation dynamics and microstructure in magnetocaloric MnCoGe thin films grown on two different substrates (Si or Ge). All the films show a hexagonal structure at room temperature, being polycrystalline when grown on Si substrates or displaying highly textured columnar grains with same orientation when grown on Ge substrates. Their static and dynamic magnetic properties present anomalies at lower temperature, with pronounced or singular features observed only for the highly textured samples : a significant modification of the magnetisation dynamics, as a large decoherence of the uniform resonance mode measured by ferromagnetic resonance (FMR) is found between 200 K and 10 K, when the magnetic field is applied normal to the surface, pointing to a spin order transition or a distorted structure with a canted spin arrangement. Below a freezing temperature, typical features of spin-glass like non-equilibrium dynamics are noted in the magnetic relaxation and memory effects suggesting magnetic frustration and disorder. In addition, the in-plane angular dependence of the resonance field displays a partial transition from the hexagonal phase below 200 K that can be attributed to the distortion of the hexagonal lattice with a canted spin arrangement observed in doped samples. The FMR linewidth increases strongly in this temperature range indicating a high magnetic damping, which is equally observed for the samples grown on Si below 40 K.

- Magnetocaloric properties and critical behavior in manganite La_0.8Sr_0.2MnO₃ link article

- Multiferroic nanofibers CFO-BCTSn link article1, article2

Moving magnetic bits in a multisegmented nanotrack

Magnetic domains are commonly used as digital bits in functional devices as hard disks. The magnetic domains are separated by transition regions ("domain walls") in which the magnetic moments change orientation by 180°. The standard device operations are based on the systematic motion of such domain walls on the magnetic track. Numerical simulations were conducted on domain wall motion, when current pulses were applied, in a nanotrack composed of different materials. We determine a complex domain wall motion with exotic magnetic textures as vortices or antivortices that emerge at the interfaces crossing. A particularity of the motion is the 180° rotation of the domain walls from one region to another, depending on the applied pulse and material parameters, which could lead to encoding information into domain wall orientation. (from Domain-wall dynamics in multisegmented Ni/Co nanowires in Phys. Rev. B 103, 054435 (2021) DOI: https://link.aps.org/doi/10.1103/PhysRevB.103.054435 )

Recent Publications: Analytical description of the topological interaction between magnetic domain walls in nanowires in Phys. Rev. B 101, 014438 (2020)

Special Issue for Materials journal open for submissions: www.mdpi.com/si/72914