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DTSTART;TZID=Europe/Paris:20260612T140000
DTEND;TZID=Europe/Paris:20260612T160000
DTSTAMP:20260617T164412
CREATED:20260604T141732Z
LAST-MODIFIED:20260604T141732Z
UID:10000186-1781272800-1781280000@sfp-alpes.fr
SUMMARY:Soutenance de Thèse de Giovanni OLIVETTI (CEA-Irig / Spintec)
DESCRIPTION:Angular Momentum Transfer Between Waveforms in Axisymmetric Geometries\nRésumé : \nThis thesis investigates the role of angular momentum transfer in the coupling between elastic and spin excitations in magneto-mechanical systems. \nIn axisymmetric geometries\, rotational invariance provides the natural framework for the conservation of total angular momentum[1]. In such a case\, this quantity unambiguously labels the eigenmodes of the system and constrains their coupling to an external excitation through well-defined selection rules[2]. The manuscript develops this physical picture from a general perspective based on Noether’s theorem\, it introduces spin and orbital angular momentum contributions for a generic vector field and proposes an analytical description of magneto-elastic coupling in axisymmetric systems. \nThis framework is then applied to two complementary experimental platforms realized in the context of this doctoral work. The first combines chiral surface-acoustic excitations with a magnetic vortex texture in a patterned ferromagnetic disk. The second consists of partially suspended axisymmetric YIG microresonators\, designed to support both low-loss mechanical motion and confined spin dynamics within the same structure[3]. Together\, these two systems provide complementary routes to investigate how elastic and magnetic modes carrying angular momentum can be generated\, controlled\, and coupled in realistic devices. \nIn particular\, this work demonstrates the controlled excitation and optical mapping of a surface-acoustic vortex by means of spiral interdigitated transducers. It further addresses the stabilization of magnetic vortex textures in micrometer-scale ferromagnetic disks on anisotropic piezoelectric substrates\, as well as their positioning at the center of elastic rotation. The coupling strength in suspended axisymmetric YIG microresonators has been evaluated by comparing experimental data with theoretical modeling\, indicating a weak-coupling regime. Moreover\, the role of weak symmetry breaking has been discussed for the selective excitation of counter-propagating elastic modes that would otherwise be degenerate. \nThese developments establish several of the physical and technological conditions required to address experimentally the coupling of elastic and spin excitations carrying angular momentum. More broadly\, they outline a route toward magneto-elastic platforms in which symmetry can be used as a resource for selective excitation. In this perspective\, partially suspended magnetic microresonators may provide a promising route toward strong magnon-phonon coupling under geometrical and symmetry constraints directly relevant for coherent functionalities. In the longer term\, such systems could serve as building blocks for mode-selective transducers and hybrid architectures combining magnetic\, elastic\, and optical degrees of freedom\, with possible perspectives for microwave-to-optical coherent transduction[4]. \nReferences \n\nGaranin & Chudnovsky\, Phys. Rev. B 92\, 024421 (2015).\nAn et al.\, Phys. Rev. B 101\, 060407 (2020).\nHeyroth et al.\, Phys. Rev. Appl. 12\, 054031 (2019).\nEngelhardt et al.\, Phys. Rev. Appl. 18\, 044059 (2022). ​\n\n\n\nPlus d’information\n​ \nPour suivre la soutenance ​​​en visioconférence​ ​​: lien à venir\n\n\n\n\nAccess to the CNRS site is restricted. Please contact Olivetti Giovanni​  or Benjamin Pigeau at least 48h before the defense if you need an entry clearance. You just need to communicate your name and surname\, and you will receive the entry clearance by email.
URL:https://sfp-alpes.fr/event/soutenance-de-these-de-giovanni-olivetti-cea-irig-spintec/
LOCATION:CNRS – Bâtiment A\, CNRS - Institut Néel 25 avenue des Martyrs\, Grenoble\, 38054\, France
CATEGORIES:Soutenance,Soutenance de Thèse
ORGANIZER;CN="IRIG - CEA":MAILTO:odile.rossignol@cea.fr
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260618T140000
DTEND;TZID=Europe/Paris:20260618T160000
DTSTAMP:20260617T164412
CREATED:20260529T144049Z
LAST-MODIFIED:20260529T145529Z
UID:10000174-1781791200-1781798400@sfp-alpes.fr
SUMMARY:Soutenance HDR de Rebekka WILD (IRIG / IBS)
DESCRIPTION:Molecular insight into the wonderful complex world of protein glycosylation\nRésumé : \nThis research habilitation focuses on the characterization of a class of enzymes – glycosyltransferases – that are involved in the biosynthesis of glycoproteins. It emphasizes the use of cryo-electron microscopy (cryo-EM) to study these enzymes\, for which obtaining mechanistic insights remains a challenging task to this day. The presentation will provide an overview of the different types of glycosylation found in humans\, along with a detailed description of the biosynthetic pathways of N-linked glycans and glycosaminoglycans. Subsequently\, I describe my work over the past ten years\, which is divided into two parts : my postdoctoral studies on a central enzyme complex of the N-linked glycosylation machinery and the work of my research team at the Institut de Biologie Structurale focusing on heparan sulfate and chondroitin sulfate biosynthesis. It closes with an overview on ongoing and future projects.​ \nL’accès au campus EPN nécessite un avis de rendez-vous. Merci d’adresser votre demande à ibs.seminaires@ibs.fr au moins 48h à l’avance. \n\nN’oubliez pas de vous munir d’une pièce d’identité.​
URL:https://sfp-alpes.fr/event/rebekka-wild-irig-ibs/
LOCATION:IBS – Salle des séminaires\, IBS 71 avenue des Martyrs\, Grenoble\, 38042\, France
CATEGORIES:Soutenance,Soutenance HDR
ORGANIZER;CN="IBS":MAILTO:ibs.seminaires@ibs
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260618T141500
DTEND;TZID=Europe/Paris:20260618T163000
DTSTAMP:20260617T164412
CREATED:20260529T150859Z
LAST-MODIFIED:20260529T150945Z
UID:10000177-1781792100-1781800200@sfp-alpes.fr
SUMMARY:Soutenance de HDR de Andrew GROSS (DCM (équipe BIOCEN))
DESCRIPTION:Nanostructured porous frameworks to control and drive bioelectrocatalysis for sensing and energy generation\n_ \n Contact : Nathalie.Camerino@univ-grenoble-alpes.fr \n 
URL:https://sfp-alpes.fr/event/soutenance-de-hdr-de-andrew-gross-dcm-equipe-biocen/
LOCATION:DCM – Bât Nanobio\, DCM 570 rue de la Chimie\, St Martin d'Hères\, 38400\, France
CATEGORIES:Soutenance,Soutenance HDR
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260619T100000
DTEND;TZID=Europe/Paris:20260619T110000
DTSTAMP:20260617T164412
CREATED:20260529T130829Z
LAST-MODIFIED:20260529T130829Z
UID:10000169-1781863200-1781866800@sfp-alpes.fr
SUMMARY:Soutenance HDR de Julien PERARD (Irig/LCBM)
DESCRIPTION:From iron to biohydrogen: how bacteria are inspiring the biotechnologies of tomorrow\nRésumé : \nMicroorganisms play a crucial role in biotechnologies\, enabling the transformation of matter into high-value gases and biomass. At a time when the climate emergency demands a rethinking of our energy models\, my work is part of a responsible research approach\, aiming to reconcile scientific excellence\, environmental sustainability\, and economic viability.​\nOver the past twelve years\, I have dedicated my career to understanding the molecular mechanisms of the Fur and SUF systems (Fe-S cluster biogenesis\, bacterial virulence) and to studying nickel insertion into CO dehydrogenase\, using integrated structural approaches (SAXS\, MALLS\, crystallography). Since 2021\, I have refocused my research on energy biotechnologies. After a brief overview of my scientific journey\, I will detail my projects on developing solutions for BioH₂ production and CO₂ valorization\, particularly through the « Bioraffinery » project (combining photofermentation and methanogenesis)\, inspired by my participation in the 2022 EIC Horizon Prize. I have optimized photobioreactors (PBRs)\, improving their light efficiency and achieving up to 5 mol H₂/mol of substrate from PLA waste.​\nToday\, I am working on optimizing microbial strains and culture conditions\, as well as integrating circular processes for the joint production of BioH₂/BioCH₄. In collaboration with Génoscope\, CEA Tech\, and industrial partners\, I have developed advanced biorafineries to convert by-products into biofuels.​\nMy work\, at the interface of biophysics\, enzymology\, and engineering\, is part of a decarbonized bioeconomy approach.​ \n_ \nContact : alain.farchi@cea.fr
URL:https://sfp-alpes.fr/event/soutenance-hdr-de-julien-perard-irig-lcbm/
LOCATION:DCM – Bât Nanobio\, DCM 570 rue de la Chimie\, St Martin d'Hères\, 38400\, France
CATEGORIES:Soutenance,Soutenance HDR
ORGANIZER;CN="IRIG - CEA":MAILTO:odile.rossignol@cea.fr
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260619T140000
DTEND;TZID=Europe/Paris:20260619T160000
DTSTAMP:20260617T164412
CREATED:20260529T145132Z
LAST-MODIFIED:20260529T145509Z
UID:10000175-1781877600-1781884800@sfp-alpes.fr
SUMMARY:Soutenance de Thèse de Marco BIAGI (IRIG/Spintec)
DESCRIPTION:Exploration of orbital-to-spin conversion materials and integration in 3-terminal spin-orbit torque magnetic tunnel junctions\nRésumé : \nThe development of electrically controlled nanomagnets for spintronic applications\, particularly non-volatile magnetic memories (MRAM)\, is attracting strong interest due to the limitations of CMOS-based memories such as SRAM and eDRAM. Spin–orbit torque (SOT) MRAMs are promising candidates for addressing SRAM specifications; however\, current materials still suffer from limited efficiency and high resistivity\, leading to unmet write-current requirements. Recently\, studies have highlighted orbital phenomena as a potential route to enhance SOT efficiency\, owing to their larger magnitudes and availability in a broader set of materials. However\, orbital currents do not couple to magnetization in the absence of spin–orbit coupling\, requiring an orbital-to-spin conversion layer\, which motivates studies of conversion mechanisms and associated physics. \nIn this PhD work\, we evaluate promising orbital/HM/FM material systems for SOTMRAM applications. We present a comprehensive study of Ru/HM/FeCoB and Ta/W/ FeCoB systems\, where Ru and Ta act as orbital current sources\, while Ta\, W\, and Pt serve as orbital-to-spin conversion layers. Ru is predicted to exhibit one of the largest orbital Hall angles among transition metals while maintaining low resistivity. Ta\, a heavy metal with a large spin Hall effect\, is predicted to exhibit an orbital Hall angle approximately one order of magnitude larger than its spin counterpart. When a heavy metal is used as a conversion layer\, multiple spin-current contributions can coexist and add linearly to the total effective spin Hall conductivity\, potentially enhancing the overall SOT efficiency. \nWe characterized key parameters relevant to SOT magnetic tunnel junctions (MTJ) devices\, including saturation magnetization\, effective anisotropy field\, and resistivity\, and we quantified damping-like (ξDL) and field-like (ξFL) SOT efficiencies as a function of orbital and conversion layer thickness\, both in as-deposited and 300°C annealed samples. These metrics are benchmarked against reference HM/FeCoB systems to isolate the effect of the additional orbital layer. For Ru/Ta and Ru/W stacks\, limited enhancement ξFL of ξDL is observed relative to reference systems. In contrast\, Ru/Pt exhibits a twofold increase in ξDL compared to Pt alone. This difference is attributed to the stronger SOC in Pt\, which enables more efficient orbital-to-spin conversion. The independence of ξDL on Ru thickness further suggests an interfacial origin of the orbital contribution in Ru/Pt. However\, thermal annealing strongly degrades ξDL\, limiting its applicability for SOT-MRAM. In Ta/W systems\, we observe a strong enhancement of ξDL by a factor of 4.4 relative to Ta and 3.2 relative to W. A parallel-resistor model indicates that conventional SHE contributions cannot fully account for this increase\, pointing to an additional orbital-related mechanism. Extending the study to 400 °C annealing shows that ξDL remains largely stable\, indicating good thermal robustness while maintaining perpendicular magnetic anisotropy. \nLeveraging these advantages\, we further integrate the Ta/W system into SOT-MTJs and benchmark it against standard W-based MTJs. We investigate the pulse-length dependence of the critical switching current and provide a first demonstration of integrated orbital-to-spin conversion in SOT-MTJs. Ta/W devices exhibit switching currents comparable to W-based devices but have a lower switching current density and improved perpendicular magnetic anisotropy stability. Finally\, we present a proof-of-concept for vertical non-local switching of SOT-MTJ using orbital torques\, simplifying bottom-pinned SOT-MRAM fabrication. Overall\, these results demonstrate that orbital physics can be exploited to enhance SOT-MTJ performance\, simplify fabrication\, and provide a promising route toward scalable bottom-pinned MRAM technologies. \nPlus d’information : https://www.spintec.fr/phd-defense-exploration-of-orbital-to-spin-conversion-materials-and-integration-in-3-terminal-spin-orbit-torque-magnetic-tunnel-junctions/ \nPour suivre la soutenance ​​​en visioconférence : https://univ-grenoble-alpes-fr.zoom.us/j/98769867024?pwd=dXNnT3RMeThjYStybGVQSUN0TVdJdz09 \n_ \n\n\nP​resential access to the confere​nce room at CEA in Gre​​noble requires an entry authorization\, request to admin.spintec@cea.fr
URL:https://sfp-alpes.fr/event/soutenance-de-these-marco-biagi-irig-spintec/
LOCATION:CEA – Salle de Séminaire IRIG (1005 – 445)\, Laboratoire Irig/Spintec\, salle de séminaire 445\, bâtiment 1005\, CEA-Grenoble\, Grenoble
CATEGORIES:Soutenance,Soutenance de Thèse
ORGANIZER;CN="IRIG - CEA":MAILTO:odile.rossignol@cea.fr
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260622T133000
DTEND;TZID=Europe/Paris:20260622T153000
DTSTAMP:20260617T164412
CREATED:20260604T143528Z
LAST-MODIFIED:20260604T143528Z
UID:10000188-1782135000-1782142200@sfp-alpes.fr
SUMMARY:Soutenance de Thèse de Khadeeja MUBASHIRA (CEA-Irig/IBS)
DESCRIPTION:Étude de la séparation de phase de la phosphoprotéine du virus de la rage et de sa régulation par LC8\nRésumé : \nRabies virus (RABV) replication occurs in cytoplasmic\, membrane-less compartments known as Negri bodies (NBs)\, formed through liquid-liquid phase separation (LLPS) of viral components. The phosphoprotein (RABV P) is a central\, intrinsically disordered scaf fold of the viral replication machinery. This thesis investigates the structural\, biophysical\, and dynamic properties of RABV P\, with emphasis on its phase separation behavior and interactions with molecular partners. To enable this\, recombinant expression and purification protocols were optimized to produce stable\, high-quality protein samples for reproducible analyses. \nWe first characterized the intrinsic phase behavior of RABV P in vitro. The protein undergoes thermoresponsive LLPS with a lower critical solution temperature (LCST)\, forming reversible condensates within a narrow range of protein and salt concentrations. This process is driven by multivalent interactions within a heterogeneous ensemble of conformations\, where dimers assemble into higher-order oligomers prior to phase separation. The resulting phase diagram reveals a complex\, reentrant system governed by a balance between electrostatic repulsion and attractive dipole-dipole interactions. \nThe role of ionic conditions was further examined. While NaCl induced reentrant phase separation\, LLPS strongly depended on ion identity rather than ionic strength alone. Chloride salts promoted condensate formation\, whereas bromide salts did not\, indicating ion-specific (Hofmeister-type) effects. Systematic trends showed that fluoride enhances phase separation\, while cation effects are weaker. Divalent ions also promoted LLPS\, highlighting valency contributions. Chemical perturbations confirmed that condensates are stabilized by weak interactions: 1\,6-hexanediol partially disrupted droplets\, whereas ATP fully dissolved them. Notably\, RABV P intrinsically phase separates even in water\, modulated by pH\, protein concentration\, and ionic conditions. \nTime-resolved small-angle X-ray scattering (SAXS) revealed the structural evolution underlying LLPS. Following a temperature jump\, RABV P undergoes a hierarchical assembly process\, transitioning from dispersed species to larger structures. Early conformational rearrangements precede the formation of intermediate clusters\, followed by growth into larger assemblies. These structures remain disordered and liquid-like\, supporting a multistep nucleation-and-growth mechanism. \nThe host protein LC8 was investigated as a regulator of RABV P condensation. LC8 binds a conserved motif in RABV P with high affinity\, forming a defined complex and partitioning into condensates. Functionally\, LC8 enhances phase separation by increasing condensate size\, enriching RABV P in the dense phase\, and broadening the phase-separation window. It shifts phase boundaries toward lower concentrations and temperatures while preserving liquid-like properties. These results indicate that LC8 actively promotes condensation by stabilizing interaction-competent conformations and enhancing intermolecular connectivity. \nTo assess whether LC8 can compensate for intrinsic multivalency\, a truncated RABV P lacking the dimerization domain was analyzed. Although LC8 bound this construct\, the interaction was weaker and failed to restore robust phase separation. Only weak condensation was observed under crowding conditions\, demonstrating that LC8 cannot substitute for the native dimerization-driven multivalency.\nOverall\, this work establishes RABV P as a finely tuned multivalent scaffold whose phase behavior arises from the interplay of intrinsic disorder\, ion-specific effects\, and hierarchical assembly. LLPS emerges as a multistep\, non-ideal process rather than a simple binary transition. LC8 acts as a key host regulator that enhances phase separation without altering condensate dynamics\, while intrinsic multivalency remains essential. These findings provide a mechanistic framework for understanding viral condensate formation and highlight potential avenues for antiviral intervention. \n_ \nContact : alain.farchi@cea.fr
URL:https://sfp-alpes.fr/event/soutenance-de-these-de-khadeeja-mubashira-cea-irig-ibs/
LOCATION:Amphi A de Biologie\, Rue de la Piscine\, Saint-Martin-d'Hères\, 38400\, France
CATEGORIES:Soutenance,Soutenance de Thèse
ORGANIZER;CN="IRIG - CEA":MAILTO:odile.rossignol@cea.fr
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260623T140000
DTEND;TZID=Europe/Paris:20260623T160000
DTSTAMP:20260617T164412
CREATED:20260604T144948Z
LAST-MODIFIED:20260604T144948Z
UID:10000190-1782223200-1782230400@sfp-alpes.fr
SUMMARY:Soutenance HDR de Damien CALISTE (CEA-Irig/MEM)
DESCRIPTION:Étude de mécanismes à l’échelle atomique pour les matériaux fonctionnels\, apports de la DFT comme un outils en évolution\nRésumé : \nThe purpose to use numerical tools is to treat problems where the analytical solutions are too complex or unknown. In the field of solid-state physics\, the advent of the Density Functional Theory (DFT) had a major impact on the studies of materials at the atomic scale. Its numerous implementations and ability to efficiently run on large computing infrastructures\, made it popular and it quickly became indispensable in both academic and industrial research\, enabling unprecedented insights into the electronic\, structural\, and chemical properties of complex systems. However\, the power of DFT is not solely derived from its theoretical foundations; it is equally dependent on the robustness\, efficiency\, and adaptability of the computational tools that implement it. ​ \nThis defense will deal with these two aspects: material science through DFT simulations\, and maintainance and development of large numerical infrastructures like a DFT code. ​ \nI will first address how atomistic-level simulations can be used to complement experimental characterisations\, through the example of the indirect role played by Se atoms in the efficiency improvement of CdTe solar panels. Revealing such mechanisms is important for material design\, driving material engineering by knowledge. ​ \nA second part will be dedicated to a broad overview on the physics description of a graphite electrode in a Li-ion battery. Starting from a fully charged anode\, and following the deintercalation process\, I will question what insights we can get from DFT calculations with the existing knowledge obtained from long-passed experiments as from more recent in-operando characterisation results. ​ \n​Studying the dilute regime in graphite intercalation will lead to open questions about the capability of numerical simulations to address cases where the strong interactions between the cations and the host material\, compete with the binding of the layers. To properly address such questions\, it is important to have available within DFT\, a level of theory capable of treating inhomogeneous systems made of places where covalent bonds are dominant while in other areas van der Waals interactions take the lead. These situations can be commonly found in several classes of materials\, from van der Waals heterostructures to hybrid perovskites when out-of-equilibrium processes take place\, with defect / impurity diffusion or phase / structural transitions. The recent developments of versatile meta-GGAs associated to dispersion corrections\, look promising and have demonstrated their ability to reproduce perfect van der Waals systems. Concurrently\, their usage are restricted to some codes\, hindered by the complexity in DFT implementations\, isolating the diffusion of new ideas. I believe that the advent of code generation through AI is a timely opportunity to help spreading state-of-the-art DFT developments. Such thoughts will be discussed in the last part of the defense.​ \n_ \nContact : alain.farchi@cea.fr
URL:https://sfp-alpes.fr/event/soutenance-hdr-de-damien-caliste-cea-irig-mem/
LOCATION:CEA\, entrée principale – Salle de soutenance (bâtiment A2)\, 17\, avenue des Martyrs\, Grenoble\, 38000\, France
CATEGORIES:Soutenance,Soutenance HDR
ORGANIZER;CN="IRIG - CEA":MAILTO:odile.rossignol@cea.fr
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260626T140000
DTEND;TZID=Europe/Paris:20260626T160000
DTSTAMP:20260617T164412
CREATED:20260529T140204Z
LAST-MODIFIED:20260529T140307Z
UID:10000170-1782482400-1782489600@sfp-alpes.fr
SUMMARY:Soutenance de Thèse de Henri GRÖGER (Irig/IBS)
DESCRIPTION:Structural and functional characterisation of the vaccinia virus PLD- fold endonuclease K4\, telomere-binding protein i1 and the DNA polymerase complex E9A20D4\nRésumé : \n\nPoxviruses\, such as the vaccinia virus (VACV) and the monkeypox virus\, are large\, enveloped dsDNA viruses from the orthopoxvirus genus that replicate entirely within the host cytoplasm. The 2022 and 2024 outbreaks of mpox\, caused by clade IIb and Ib\, respectively\, have revealed the lack of efficient antivirals and underlined the urgency of understanding poxvirus biology. The poxvirus genome is flanked by short\, inverted complementary hairpin telomeres that feature mismatched bases and insertions essential for viral replication. ​\n​\nThis thesis presents the structural and functional characterisation of three proteins central to poxvirus DNA metabolism : the E9A20D4 DNA polymerase holoenzyme\, and two telomere-interacting proteins\, the PLD-fold nuclease K4 and I1. The project initially focused on the VACV polymerase holoenzyme\, but was reoriented towards the telomere-interacting proteins following the publication of numerous competing mpox polymerase structures. ​\n​\nHaving established that VACV polymerase activity requires K+ and is inhibited by Na+\, I undertook a structure determination of the E9A20D4 polymerase holoenzyme bound to template DNA\, primer and incoming nucleotide in the presence of K+\, using single-particle cryogenic electron microscopy (cryo-EM). I obtained both the structure of the complex E9exo−A20D4 as well as the structure of E9exo− alone bound to the primer-template DNA. The structures in the presence of K+ appear identical to published structures in the presence of Na+. However\, I identified an ion binding site in the exonuclease domain of E9. The thumb domain is disordered in the DNA-free structure\, partially disordered in DNA-bound E9 and ordered in the holoenzyme-DNA complex. SAXS data indicate conformational flexibility\, with more open conformations of E9A20D4 lacking an E9-D4 interface\, while mass photometry reveals partial dissociation of E9A20D4 at low concentrations\, even in the presence of substrate. ​\n​\nUsing cryo-EM\, I report the first structures of K4 in both apo and DNA-bound states\, revealing that the active site is occluded by an orthopoxvirus-specific C-terminal extension of the PLD fold that is displaced upon DNA binding. Biochemical characterisation demonstrates that K4 functions as a DNA-specific endonuclease with a preference for single-stranded DNA and hairpin loops. ​\n​\nI also report the first cryo-EM structure of I1 bound to DNA. I1 is known to bind to viral telomeres and is essential for virion maturation. Cryo-EM data showed the presence of dimers where the head domains 2 and 3 of I1 interact with the DNA duplex through electrostatic interactions\, while the N-terminal domain predicted to be α-helical remains disordered. In solution\, isolated I1 or I1 bound to DNA forms higher-order assemblies\, predominantly tetramers\, but also octamers. ​\n​\n​ Altogether\, these findings substantially advance the molecular understanding of poxvirus biology\, providing a foundation for future mechanistic studies and the rational development of antiviral strategies against emerging orthopoxvirus infections.\n​​\n\n\nLes séminaires et soutenances sont ouverts à tous\, notez toutefois que l’accès au campus EPN nécessite un avis de rendez-vous. Merci de remplir ce formulaire  et de l’adresser\, plus de 48h à l’avance\, à ibs.seminaires@ibs.fr. Pensez à vous munir d’une pièce d’identité le jour de votre visite.\n\n  \n  \n  \n  \n  \n 
URL:https://sfp-alpes.fr/event/soutenance-de-these-de-henri-groger-irig-ibs/
LOCATION:Salle des séminaires du CIBB\, EPN Campus - 71 avenue des Martyrs\, Grenoble\, 38000\, France
CATEGORIES:Soutenance,Soutenance de Thèse
ORGANIZER;CN="IRIG - CEA":MAILTO:odile.rossignol@cea.fr
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260707T140000
DTEND;TZID=Europe/Paris:20260707T160000
DTSTAMP:20260617T164412
CREATED:20260611T110542Z
LAST-MODIFIED:20260611T110651Z
UID:10000196-1783432800-1783440000@sfp-alpes.fr
SUMMARY:Soutenance de Thèse par Hanna KARAOUI (CEA-Irig/Spintec)
DESCRIPTION:Perpendicular anisotropy interfaces for high-efficiency low power spintronics\nRésumé : \nL’augmentation de la consommation mondiale d’énergie accentue le besoin de stockage de données à haute efficacité\, orientant la recherche vers des mémoires non volatiles à faible puissance comme la MRAM (Magnetoresistive Random Access Memory) à couple de transfert de spin. Les jonctions tunnel magnétiques (MTJ) perpendiculaires conventionnelles font face à un compromis critique lors de la réduction d’échelle\, l’anisotropie magnétique d’interface diminue\, imposant un dilemme entre stabilité thermique et efficacité de commutation. Les structures doubles-MTJ (DMTJ) répondent théoriquement à ce problème en insérant la couche de stockage (SL) entre deux barrières de MgO\, bien qu’elles souffrent souvent d’une fabrication complexe et de l’instabilité des couches de référence supérieures. Cette thèse étudie une architecture innovante nommée ASL-DMTJ\, où le polariseur fixe supérieur est remplacé par une couche d’assistance magnétique (ASL) à aimantation libre. Cette ASL interagit dynamiquement avec la couche de stockage par couple de transfert de spin et couplage ferromagnétique\, renforçant la stabilité par alignement magnétostatique et permettant une rétention élevée ainsi qu’une commutation à très faible puissance. Afin d’évaluer les performances via l’intégration de cette ASL\, un cadre de modélisation macrospin complet a été établi pour étudier les propriétés magnétostatiques et dynamiques. L’analyse du profil énergétique démontre que la stabilité thermique du système dépend de l’anisotropie interfaciale liée à l’épaisseur et du couplage dipolaire mutuel. Tandis que la réduction de l’épaisseur de la SL diminue intrinsèquement la barrière d’énergie\, l’inclusion du couplage dipolaire renforce la stabilité globale en favorisant les configurations parallèles\, agissant comme un mécanisme vital pour la rétention des données. Des investigations numériques mettent en évidence un mécanisme de commutation par étapes où la SL bénéficie des couples cumulatifs fournis par les couches de référence et d’assistance\, garantissant que la SL reste la couche la plus stable tandis que l’ASL facilite le renversement. Sur le plan expérimental\, une étude comparative démontre que les structures à double MgO offrent des propriétés de transport nettement améliorées par rapport aux implémentations à triple MgO en éliminant la résistance parasite. En optimisant l’épaisseur et l’oxydation de la barrière tunnel\, des valeurs de magnétorésistance tunnel optimisées ont été obtenues. L’utilisation systématique d’échantillons en double-MgO avec l’interface inférieure FeCoB/MgO sert de barrière principale\, tandis que l’interface supérieure est cruciale pour maximiser le champ d’anisotropie effectif. L’optimisation des matériaux a confirmé que les échantillons conservant une couche magnétique à l’interface MgO supérieure offrent une stablité dépassant le seuil de stabilité thermique requis de 40kBT avec une symétrie de commutation élevée. Enfin\, l’efficacité de commutation a été quantifiée via les distributions du taux d’erreur d’écriture sur des impulsions allant de 4 ns à 10 µs. Nous avons introduit un modèle unifié capturant la dépendance de la tension critique par rapport à la largeur d’impulsion à travers les régimes balistiques et thermiquement assistés. Ce modèle identifie un seuil de commutation caractéristique centré sur le point d’énergie minimale\, introduisant une nouvelle figure de mérite\, le rapport entre la barrière de stabilité thermique et l’énergie de commutation minimale\, fournissant une estimation plus précise de l’énergie opérationnelle. Les résultats expérimentaux ont montré une dépendance linéaire de la barrière d’énergie vis-à-vis du diamètre\, prouvant un mécanisme de commutation régi par la nucléation de domaines et la propagation de parois plutôt que par un modèle macrospin pur. Les calculs analytiques et expérimentaux confirment que les champs de fuite de la couche de référence modulent significativement ces barrières. \nLa hausse de la consommation énergétique mondiale pousse au développement de mémoires plus sobres comme la MRAM (Magnetoresistive Random Access Memory). Mais en dessous de 20 nm\, les jonctions magnétiques classiques perdent en stabilité ou en efficacité. Cette thèse étudie une architecture innovante\, appelée ASL-DMTJ\, où une couche magnétique d’assistance aide la couche de stockage à conserver l’information tout en facilitant l’écriture avec peu d’énergie. Des modèles montrent que les interactions magnétiques internes renforcent la stabilité malgré la miniaturisation. Les expériences confirment que des structures à double barrière MgO améliorent les performances et réduisent les pertes. Un nouveau modèle de commutation est aussi proposé pour mieux estimer l’énergie nécessaire. Ces travaux ouvrent la voie à des mémoires plus petites\, rapides et économes en énergie.Face à l’explosion de la consommation numérique\, nos appareils ont besoin de mémoires plus économes. La technologie MRAM est une candidate idéale car elle conserve les données sans électricité. Cependant\, miniaturiser ces mémoires réduit leur stabilité \, les données risquent de s’effacer. Cette thèse explore une architecture innovante\, la “ASL-DMTJ”. L’idée est d’entourer la couche de stockage d’informations par deux barrières protectrices et d’ajouter une couche d’assistance magnétique. Cette dernière agit comme un guide dynamique qui aide à l’écriture des données tout en renforçant leur maintien dans le temps. En combinant simulations numériques et tests réels\, ces travaux prouvent que ce design permet de créer des mémoires ultra-stables et rapides. L’étude montre aussi que le basculement de l’information se passe à point d’énergie minimale\, offrant une grande efficacité énergétique. Ce nouveau modèle architectural permet d’envisager des technologies dont la consommation électrique serait drastiquement réduite. \nPlus d’information \nPour suivre la soutenance ​​​en visioconférence zoom​  ​​ –  Meeting ID : 987 6986 7024 – Passcode : 025918​ \n_ \n\n\nATTENTION ! L’entrée du site CEA-Grenoble nécessite une autorisation préalable et sur présentation de votre pièce d’identité le jour de votre venue (CI ou passeport\, car le permis de conduire n’est pas recevable).\nVeuillez impétaivement nous contacter par mail avant le 26 juin : admin.spintec@cea.fr​Note: Entry to the CEA-Grenoble site requires prior authorization and the presentation of your ID on the day of your visit (ID card or passport; driver’s licenses are not accepted).\nPlease request this authorization before June 26th to admin.spintec@cea.fr​
URL:https://sfp-alpes.fr/event/soutenance-de-these-par-hanna-karaoui-cea-irig-spintec/
LOCATION:CEA – Salle de Séminaire IRIG (1005 – 445)\, Laboratoire Irig/Spintec\, salle de séminaire 445\, bâtiment 1005\, CEA-Grenoble\, Grenoble
CATEGORIES:Soutenance,Soutenance de Thèse
ORGANIZER;CN="IRIG - CEA":MAILTO:odile.rossignol@cea.fr
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