https://www.spintec.fr/wp-content/uploads/2025/10/Plaquette_Spintec_2026.pdf
Context
Magnetic skyrmions in thin films are spin textures across which magnetization follows a cycloid with a unique sense of rotation, called chirality. This specific magnetic configuration can be stabilized in ferromagnetic thin films, sandwiched between films of a heavy metal and an oxide, and which presents large interfacial perpendicular magnetic anisotropy (PMA). Additionally, the lack of inversion symmetry allows an antisymmetric exchange interaction called interfacial Dzyaloshinskii-Moriya (DMI). Since skyrmions are topological solitons that can be moved by electrical current, they are currently attracting considerable interest both for the underlying physics and for their applicative potential. In this project, we investigate β-phase tungsten (β-W) as a replacement for Ta in Ta/FeCoB/TaOx stacks popular for skyrmion based devices. With its large spin Hall angle, β-W is expected to enhance spin-orbit torque (SOT) efficiency, enabling more reliable nucleation, manipulation, and detection of skyrmions. To establish a detailed understanding of skyrmion - SOT interactions in β-W heterostructures, we will perform quantitative studies of SOT effective fields using harmonic Hall measurements. Building on this platform, we will combine high-efficiency SOT from β-W with voltage control enabled by lithium phosphorous oxynitride (LiPON). In collaboration with CEA-LETI, which provides the required LiPON deposition and testing facilities, we will integrate a solid-state magneto-ionic layer directly into skyrmion-hosting heterostructures. Li-ion intercalation through LiPON allows reversible tuning of interfacial spin-orbit coupling and PMA, offering deterministic control over skyrmion chirality, size, and stability. This dual control approach with β-W for strong SOT actuation and LiPON for low-power ionic gating creates a versatile materials platform to engineer programmable skyrmion dynamics. This will be exploited to probe noise signatures, benchmark energy-efficient skyrmion manipulation, and ultimately develop voltage-programmable skyrmion sensors and computing devices.
Work program & Skills acquired during internship
Within this project, the M2 student will develop material platforms for skyrmion control by combining high-efficiency spin-orbit torques (SOT) with voltage driven magneto-ionics.
• Optimize β-W/FeCoB/TaOx stacks as skyrmion platforms, using Kerr microscopy to map stability and harmonic Hall/current switching to quantify SOT.
• Integrate LiPON gating layers in collaboration with CEA-LETI to reversibly tune anisotropy and interfacial spin–orbit coupling via Li-ion intercalation.
• Characterize dual-control dynamics, combining β-W SOT and LiPON gating to tune skyrmion chirality, size, and stability, with noise measurements to assess device performance.
The M2 student will be integrated into a collaborative team, benefiting from daily supervision and regular meetings, with complementary expertise provided through the partnership with CEA-LETI.
- Requested background: Master 2 physics of condensed matter, nanophysics
- Duration: 6 months
- Start period: Feb/ March 2026
- Possibility of PhD thesis: YES