Publications HAL de la collection CHIREX

Journal articles

titre
All-optical helicity-dependent switching in NiCo2O4 thin films
auteur
Ryunosuke Takahashi, Yann Le Guen, Suguru Nakata, Junta Igarashi, Julius Hohlfeld, Grégory Malinowski, Lingling Xie, Daisuke Kan, Yuichi Shimakawa, Stéphane Mangin, Hiroki Wadati
article
Applied Physics Letters, 2025, 126 (21), ⟨10.1063/5.0253785⟩
resume
All-optical switching (AOS) involves manipulating magnetization using only a pulsed laser, presenting a promising approach for next-generation magnetic recording devices. NiCo2O4(NCO) thin films, a rare-earth-free ferrimagnetic oxide, exhibit a high Curie temperature and strong perpendicular magnetic anisotropy. This study demonstrates AOS in NCO thin films at room temperature using long-duration laser pulses and high repetition rates. Unlike previous findings, the AOS phenomena we report here are helicity-dependent and observable with an ultrashort pulsed laser. Consequently, two distinct types of AOS can be observed in a single NCO thin film, contingent on the characteristics of the laser pulses and temperature.
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Journal articles
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https://hal.univ-lorraine.fr/hal-05157541/file/212405_1_5.0253785.pdf BibTex
titre
Control of the magnetic anisotropy in multirepeat Pt/Co/Al heterostructures using magnetoionic gating
auteur
Tristan da Câmara Santa Clara Gomes, Tanvi Bhatnagar-Schöffmann, Sachin Krishnia, Yanis Sassi, Dedalo Sanz-Hernández, Nicolas Reyren, Marie-Blandine Martin, Frederic Brunnett, Sophie Collin, Florian Godel, Shimpei Ono, Damien Querlioz, Dafiné Ravelosona, Vincent Cros, Julie Grollier, Pierre Seneor, Liza Herrera Diez
article
Physical Review Applied, 2024, 21 (2), pp.024010. ⟨10.1103/PhysRevApplied.21.024010⟩
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Journal articles
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https://arxiv.org/pdf/2310.01623 BibTex
titre
Controlling Single-Pulse Magnetization Switching through Angular Momentum Reservoir Engineering
auteur
Boonthum Kunyangyuen, Grégory Malinowski, Daniel Lacour, Boris Seng, Wei Zhang, Stéphane Mangin, Julius Hohlfeld, Jon Gorchon, Michel Hehn
article
ACS Materials Letters, 2025, pp.3619 - 3625. ⟨10.1021/acsmaterialslett.5c01060⟩
resume
We report a systematic study of single-pulse all-optical switching in Co/Gd bilayers, revealing that magnetization reversal dynamics can be tuned over 3 orders of magnitude. By varying the Gd thickness or inserting a Pt spacer layer between Co and Gd, we control the angular momentum transferred from the rare-earth sublattice to the transition-metal sublattice. Our results show that when Gd is abundant and strongly coupled to Co, angular momentum is efficiently transferred during Gd demagnetization, leading to ultrafast Co reversal. Reducing the Gd thickness or introducing Pt impedes this transfer, resulting in a slow domain growth mediated reversal as observed in CoDy and CoHo alloys. So, replacing Gd with Dy or Ho rare-earth elements slows down the switching due to a reduced angular momentum transfer toward Co upon demagnetization as demonstrated in CoGdDy alloy. Our findings establish angular momentum availability and transfer pathways as key parameters governing reversal dynamics.
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Journal articles
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https://hal.science/hal-05304781/file/CoGd_Reservoir_def.pdf BibTex
titre
Determining Bandgaps in the Layered Group‐10 2D Transition Metal Dichalcogenide PtSe2
auteur
Martin Mičica, Sabrine Ayari, Minoosh Hemmat, Mehdi Arfaoui, Daniel Vala, Kamil Postava, Hadrien Vergnet, Jérôme Tignon, Juliette Mangeney, Shasha Guo, Xuechao Yu, Qi Jie Wang, Zheng Liu, Sihem Jaziri, Francesca Carosella, Robson Ferreira, Sukhdeep Dhillon
article
Advanced Functional Materials, 2024, 35 (1), pp.2408982. ⟨10.1002/adfm.202408982⟩
resume

Unlike traditional group-6 transition metal dichalcogenides (TMDs), group-10 TMDs such as PtSe 2 and PdTe 2 possess highly tuneable indirect bandgaps, transitioning from semiconducting in the near-infrared to semimetal behavior with a number of monolayers (MLs). This opens up the possibility of TMD-based mid-infrared and terahertz optoelectronics. Despite this large potential, the optical properties of such materials have shown an extremely large disparity between that predicted and measured. For example, simulations show that a few MLs is required for the semiconductor-semimetal transition, whilst tens of MLs is found experimentally. This is a result of widely used optical extrapolation methods to determine bandgaps, such as the Tauc plot approach, that are not adapted here owing to i) nearby direct transitions, ii) the material dimensionality and iii) large changes in the non-parabolic bandstructure with MLs. Here, uniquely combining optical ellipsometry to determine the complex permittivity, terahertz time resolved spectroscopy for the complex conductivity and in-depth density functional theory (DFT) simulations, it is shown that the optical properties and bandstructure can be determined reliably and demonstrate clearly that the semiconductor-semimetal transition occurs for PtSe 2 layers ≈5 MLs. The microscopic origins of the observed transitions and the crucial role of the Coulomb interaction for thin semiconducting layers, and that of interlayer van der Waals forces for multilayer semimetallic samples are also demonstrated. This work of combining complimentary experimental techniques and extensive simulations avoids the application of constrained extrapolation methods to determine the optical properties of group-10 TMDs, and will be of importance for future mid-infrared and terahertz applications.

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Journal articles
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https://hal.science/hal-04753078/file/Adv%20Funct%20Materials%20-%202024%20-%20Mi%C4%8Dica%20-%20Determining%20Bandgaps%20in%20the%20Layered%20Group%E2%80%9010%202D%20Transition%20Metal%20Dichalcogenide%20PtSe2.pdf BibTex
titre
Driving skyrmions in flow regime in synthetic ferrimagnets
auteur
Sougata Mallick, Yanis Sassi, Nicholas Figueiredo Prestes, Sachin Krishnia, Fernando Gallego, Luis M. Vicente Arche, Thibaud Denneulin, Sophie Collin, Karim Bouzehouane, André Thiaville, Rafal E Dunin-Borkowski, Vincent Jeudy, Albert Fert, Nicolas Reyren, Vincent Cros
article
Nature Communications, 2024, 15 (1), pp.8472. ⟨10.1038/s41467-024-52210-y⟩
resume
The last decade has seen significant improvements in our understanding of skyrmions current induced dynamics, along with their room temperature stabilization, however, the impact of local material inhomogeneities still remains an issue that impedes reaching the regime of steady state motion of these spin textures. Here, we study the spin-torque driven motion of skyrmions in synthetic ferrimagnetic multilayers with the aim of achieving high mobility and reduced skyrmion Hall effect. We consider Pt|Co|Tb multilayers of various thicknesses with antiferromagnetic coupling between the Co and Tb magnetization. The increase of Tb thickness in the multilayers reduces the total magnetic moment and increases the spin-orbit torques allowing to reach velocities up to 400 ms$^{-1}$ for skyrmions with diameters of about 160 nm. We demonstrate that due to reduced skyrmion Hall effect combined with the edge repulsion of the magnetic track, the skyrmions move along the track without any transverse deflection. Further, by comparing the field-induced domain wall motion and current-induced skyrmion motion, we demonstrate that the skyrmions at the largest current densities present all the characteristics of a dynamical flow regime.
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Journal articles
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https://hal.science/hal-04716010/file/s41467-024-52210-y.pdf BibTex
titre
Fast current-induced skyrmion motion in synthetic antiferromagnets
auteur
van Tuong Pham, Naveen Sisodia, Ilaria Di Manici, Joseba Urrestarazu-Larrañaga, Kaushik Bairagi, Johan Pelloux-Prayer, Rodrigo Guedas, Liliana Buda-Prejbeanu, Stéphane Auffret, Andrea Locatelli, Tevfik Onur Menteş, Stefania Pizzini, Pawan Kumar, Aurore Finco, Vincent Jacques, Gilles Gaudin, Olivier Boulle
article
Science, 2024, 384 (6693), pp.307-312. ⟨10.1126/science.add5751⟩
resume
Magnetic skyrmions are topological magnetic textures that hold great promise as nanoscale bits of information in memory and logic devices. Although room-temperature ferromagnetic skyrmions and their current-induced manipulation have been demonstrated, their velocity has been limited to about 100 meters per second. In addition, their dynamics are perturbed by the skyrmion Hall effect, a motion transverse to the current direction caused by the skyrmion topological charge. Here, we show that skyrmions in compensated synthetic antiferromagnets can be moved by current along the current direction at velocities of up to 900 meters per second. This can be explained by the cancellation of the net topological charge leading to a vanishing skyrmion Hall effect. Our results open an important path toward the realization of logic and memory devices based on the fast manipulation of skyrmions in tracks.
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Journal articles
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https://hal.science/hal-04553207/file/add5751_ArticleContent_v15_FINAL_ACCEPTED.pdf BibTex
titre
Femtosecond-laser-induced reversal in in-plane-magnetized spin valves
auteur
Jun-Xiao Lin, Yann Le Guen, Julius Hohlfeld, Junta Igarashi, Quentin Remy, Jon Gorchon, Grégory Malinowski, Stéphane Mangin, Thomas Hauet, Michel Hehn
article
Physical Review Applied, 2024, 22, pp.044051. ⟨10.1103/physrevapplied.22.044051⟩
resume
Ultrashort spin-polarized electron pulses, generated through optically driven ultrafast demagnetization, have demonstrated high efficiency in achieving magnetization reversal of a ferromagnetic layer within a few hundred femtoseconds. Previous studies have focused on magnetization reversal in perpendicularly magnetized spin valves, where the static magnetization configuration and its dynamics are strongly influenced by the substantial demagnetization field inherent in this geometry. Consequently, the impact of layer thickness on the reversal process in such configurations presents a significant challenge and has been rarely studied. Here, we investigate in-plane magnetized GdCo/Cu/ferromagnetic layer spin valves in relation to isolating the impact of the Curie temperature and the ferromagnetic layer thickness on magnetization switching. We demonstrate that the threshold laser fluence necessary for reversing the ferromagnetic layer increases with the Curie temperature and the ferromagnetic layer thickness. Additionally, our findings indicate that achieving complete reversal may require multiple pulses, with the number of pulses needed increasing with the Curie temperature and the thickness of the ferromagnetic layer. The maximum thickness of the ferromagnetic layer that allows for full reversal is limited by the Gd concentration in the GdCo spin current source layer. These results enhance our understanding of ultrafast magnetization reversal induced by ultrafast spin pumping and offer valuable insights for designing energy-efficient magnetic memory devices.
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Journal articles
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https://hal.univ-lorraine.fr/hal-04764350/file/Paper.pdf BibTex
titre
Interfacial spin-orbitronic effects controlled by different oxidation levels at the Co/Al interface
auteur
Sachin Krishnia, Libor Vojacek, Tristan da Câmara Santa Clara Gomes, Nicolas Sebe, Fatima Ibrahim, Jing Li, Luis Moreno Vicente-Arche, Sophie Collin, Thibaud Denneulin, Rafal E. Dunin-Borkowski, Philippe Ohresser, Nicolas Jaouen, André Thiaville, Albert Fert, Henri Jaffrès, Mair Chshiev, Nicolas Reyren, Vincent Cros
article
Physical Review Applied, 2025, 24, pp.024055. ⟨10.1103/gtwk-mq1y⟩
resume
Perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interactions are key interactions in modern spintronics. These interactions are thought to be dominated by the oxidation of the Co/Al interface in the archetypal platinum-cobalt-aluminum oxide system. However, in this study, we observe a double sign change in the anisotropy and about threefold variation in interfacial chiral interaction, influenced not only by the oxidation, but also by the metallic Al thickness. Contrary to previous assumptions about negligible spin-orbit effects at light metal interfaces, we observe not only strong PMA with fully oxidized Al, decreasing and turning negative (in-plane) with less oxygen at the Co/Al interface, but also that the magnetic anisotropy reverts to positive (out-of-plane) values at a fully metallic Co/Al interface. These findings suggest modification in the Co d band via Co/Al orbital hybridization, an effect supported by x-ray absorption spectroscopy and ab initio theory calculations, highlighting the key impact of strain on interfacial mechanisms at a fully metallic Co/Al interface.
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Journal articles
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https://cea.hal.science/cea-05236520/file/Interfacial%20spinorbitronic%20effects%20controlled%20with%20different%20oxidation%20levels%20at%20the%20CoAl%20interface.pdf BibTex
titre
Large exchange bias field in Pt/Co bilayers with ultrathin native oxide
auteur
Agnieszka Klimeczek, Maurizio de Santis, Aurélien Masseboeuf, Jan Vogel, Laurent Ranno, Anne Lamirand, Stefania Pizzini
article
Applied Physics Letters, 2025, 127 (1), pp.012408. ⟨10.1063/5.0275288⟩
resume
We studied the magnetic properties of a Pt/Co bilayer sample with an ultrathin cobalt layer deposited as a wedge with a thickness between 0.7 and 1.4 nm. After exposure to air, the top 0.5 nm of Co oxidizes, leading to a 0.9 nm-thick CoO surface layer. The residual metallic cobalt is still ferromagnetic at room temperature, with a strong perpendicular magnetic anisotropy even down to ≈0.2–0.3 nm thickness. These properties are conserved for several months after deposition. Anomalous Hall effect measurements show the presence of an exchange bias field and a blocking temperature between 120 and 150 K, indicating that despite being ultrathin, the CoO layer acquires antiferromagnetic order at low temperatures. We attribute the large exchange bias field (up to 0.9 T at 4 K) to the ultralow thickness of the ferromagnetic Co layer. These results show that simply exposing an ultrathin Co layer to air in order to form a native CoO oxide layer allows obtaining functional properties competing with the best reported so far for optimized Co/CoO layers and core-shell nanoparticles.
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Journal articles
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https://hal.science/hal-05160323/file/APL25-AR-03400-accepted.pdf BibTex
titre
OAM driven nucleation of sub-50 nm compact antiferromagnetic skyrmions
auteur
Sougata Mallick, Peng Ye, Willem Boutu, David Gauthier, Hamed Merdji, Manuel Bibes, Michel Viret, Karim Bouzehouane, Vincent Cros
article
Advanced Functional Materials, 2024, pp.2409528. ⟨10.1002/adfm.202409528⟩
resume
Abstract Owing to their high mobility and immunity to topological deflection, skyrmions in antiferromagnetic (AFM) systems are gaining attention as a potential solution for next‐generation magnetic data storage. Synthetic antiferromagnets (SAFs) offer a promising avenue to tune the properties of the individual magnetic layers, facilitating the conditions necessary for skyrmions to be used in practical devices. Despite recent advancements achieving fast skyrmion mobility, the nucleation of small and rigid circular skyrmions without an external field remains challenging in SAFs. Theoretical predictions suggest that optical vortex (OAM) beams can stabilize skyrmionic spin textures by transferring their spin and orbital angular momentum to the magnetic material. Here, this intriguing proposal is delved into and the creation of sub‐50 nm compact skyrmions in SAFs using OAM beams is successfully demonstrated, eliminating the need for external magnetic fields. Additionally, the results underscore the importance of beam energy and the number of pulses, as both factors play critical roles in the stabilization of these AFM skyrmionic textures. This breakthrough is significant as it paves the way for stabilizing true zero‐field skyrmions in AFM systems, where magnetization is minimally affected by external magnetic fields. This work will open a potential avenue for stabilizing small, compact skyrmions in antiferroic systems, facilitating their implementation in logic and memory devices.
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Journal articles
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https://hal.science/hal-04769717/file/SAF_Skyrmion_OAM_Willey_manuscript_28052024.pdf BibTex
titre
Observation by SANS and PNR of pure Néel-type domain wall profiles and skyrmion suppression below room temperature in magnetic [Pt/CoFeB/Ru] 10 multilayers
auteur
Victor Ukleev, Fernando Ajejas, Anton Devishvili, Alexei Vorobiev, Nina-Juliane Steinke, Robert Cubitt, Chen Luo, Radu-Marius Abrudan, Florin Radu, Vincent Cros, Nicolas Reyren, Jonathan S White
article
Science and Technology of Advanced Materials, 2024, 25 (1), ⟨10.1080/14686996.2024.2315015⟩
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Journal articles
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https://hal.science/hal-04563374/file/Ukleev_Observation%20by%20SANS%20and%20PNR%20of%20pure%20N%20el-type%20domain%20wall%20profiles%20and%20skyrmion%20suppression%20below%20room%20temperature%20in%20magnetic%20Pt%20CoFeB%20Ru%2010%20multilayers_SciT.pdf BibTex
titre
Terahertz electronic and spin currents in wafer‐scale Van der Waals Bi2Se3/WSe2 heterostructures and polymorphs
auteur
Martin Mičica, Adrien Wright, Sylvain Massabeau, Sabrine Ayari, E. Rongione, M Oliveira Ribeiro, S Husain, R Sharma, T Denneulin, R E Dunin‐borkowski, Juliette Mangeney, Jérôme Tignon, R Lebrun, H Okuno, O Boulle, A Marty, F Bonell, F Carosella, Henri Jaffrès, Robson Ferreira, Jean Marie George, Matthieu Jamet, S Dhillon
article
Advanced Materials, 2025, 2025, pp.e06031. ⟨10.1002/adma.202506031⟩
resume
Van der Waals heterostructures and polymorphs have promised the realization of artificial materials with multiple physical phenomena such as giant optical nonlinearities, spin-to-charge interconversion in spintronics and topological carrier protection, through an infinitely diverse set of 2D quantum materials and their stacking order in a single layered device. However, their exploitation for the terahertz range has been limited with most investigations based around the optical domain, owing to the use of exfoliated material that inherently limits both the dimensions of the materials and the scalability for applications. Here, the combination of terahertz electronic and spin currents is demonstrated through the realization of large area complex crystalline heterostructures of topological insulators, transition metal dichalcogenides (TMDs) and ferromagnets. This is demonstrated through down-conversion of optical beams into coherent terahertz currents, where the terahertz phase permits the decoupling of the physical phenomena, and bringing novel functionalities beyond those achievable in simple homostructures. In particular, the role of different TMD polymorphs (stacking orders -1T′, 2H, and 3R) is shown with the simple change of one atomic monolayer of the material stack entirely changing the terahertz responses -both electrical and magnetic -of the artificial material. This allows to highlight ultrafast phenomena that combine both the electronic-and spin-based processes in these structures. The importance of the crystal symmetry on the magnetic properties through proximity effects is further demonstrated, showing a nonlinearity of magnetic origin as a result of the 1T′ polymorph. As well as control of the terahertz currents through different polymorphs, this scalable integration of a set of highly diverse materials establishes a platform for next-generation 2D heterostructures that integrate photonic, electronic, and spintronic properties into device architectures.
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Journal articles
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https://hal.science/hal-05317373/file/Advanced%20Materials%20-%202025%20-%20Mi%C4%8Dica%20-%20Terahertz%20Electronic%20and%20Spin%20Currents%20in%20Wafer%E2%80%90Scale%20Van%20der%20Waals%20Bi2Se3%20WSe2.pdf BibTex
titre
Transient domain boundary drives ultrafast magnetisation reversal
auteur
Martin Hennecke, Daniel Schick, Themistoklis P H Sidiropoulos, Jun-Xiao Lin, Zongxia Guo, Grégory Malinowski, Maximilian Mattern, Lutz Ehrentraut, Martin Schmidbauer, Matthias Schnuerer, Clemens von Korff Schmising, Stéphane Mangin, Michel Hehn, Stefan Eisebitt
article
Nature Communications, 2025, 16, pp.8233. ⟨10.1038/s41467-025-63571-3⟩
resume
Light-induced magnetisation switching is one of the most intriguing and promising areas where an ultrafast phenomenon can be utilised in technological applications. So far, experiment and theory have considered the origin of all-optical helicity-independent magnetisation switching (AO-HIS) in individual magnetic films only as a microscopically local, thermally-driven process of angular momentum transfer between different subsystems. Here, we demonstrate that this local picture is insufficient and that AO-HIS must also be regarded as a spatially inhomogeneous process along the depth within a fewnanometre thin magnetic layer. Two regions of opposite magnetisation directions are observed, separated by a highly mobile boundary, which propagates along the depth of a 9.4 nm thin Gd 25 Co 75 alloy. The dynamics of this transient boundary determines the final magnetisation state as well as the speed of AO-HIS throughout the entire magnetic layer. The ability to understand the influence of nanoscale and transient inhomogeneities on ultrafast switching phenomena and more generally on phase transitions will open new routes for material design and excitation scenarios in future devices for transferring and storing information.
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Journal articles
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https://hal.science/hal-05252325/file/283-s41467-025-63571-3.pdf BibTex
titre
Using hard-x-ray photoelectron spectroscopy to measure the oxidation state of gated Co/AlO$_x$ interfaces
auteur
Cristina Balan, Johanna Fischer, Capucine Gueneau, Aymen Fassatoui, Jean-Pascal Rueff, Denis Ceolin, Maurizio de Santis, Jan Vogel, Laurent Ranno, Hélène Béa, Stefania Pizzini
article
Physical Review Applied, 2024, 21 (6), pp.064023. ⟨10.1103/PhysRevApplied.21.064023⟩
resume
The perpendicular magnetic anisotropy (PMA) of metal/ferromagnet (FM)/oxide trilayers is known to depend on the degree of oxidation of the FM/oxide interface. Among the different methods to tune the PMA, magnetoionics is emerging as a promising technique with potential applications in low-power spintronic devices. In this work, the PMA of Pt/Co/AlOx/HfO2 capacitorlike devices was gradually tuned by electric field gating. Hard-x-ray photoelectron spectroscopy (HAXPES) measurements at a synchrotron radiation source, guaranteeing tunable photon energies, a collimated beam, and a large photon flux, have allowed us to probe the composition of the cobalt ultrathin film buried below the dielectric layer of the capacitors, and its evolution upon the application of the gate voltage. The Co 2p HAXPES spectra of the gated devices were compared to those obtained for Pt/Co/AlOx reference samples, for which the PMA was controlled by tuning the Co oxidation with oxygen plasma. For similar magnetic anisotropy states, the two types of samples exhibit equivalent Co 2p HAXPES spectra, with the same weight of metallic Co and CoO signatures. These results constitute direct experimental proof that, in our integrated devices, the gate voltage modifies the PMA through the modification of the oxidation state of the buried cobalt layer driven by oxygen-ion migration.
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Journal articles
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https://hal.science/hal-04643875/file/Balan-PhysRevApplied.21.064023.pdf BibTex
titre
Visualization and characterization of arbitrarily shaped pulsed-laser spots
auteur
Yann Le-Guen, Maxime Verges, Michel Hehn, Stephane Mangin, Julius Hohlfeld
article
Physical Review Applied, 2025, 23, pp.044018. ⟨10.1103/physrevapplied.23.044018⟩
resume
A novel way to represent and analyze the contours of laser-pulse-induced domains, which reflect the position at which the laser fluence drops below a certain threshold and are measured as a function of the laser-pulse energy, is introduced. It enables the visualization and quantitative characterization of arbitrarily shaped in situ laser spots with high accuracy.
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Journal articles
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https://hal.science/hal-05252332/file/276-Spotsizepaper_PhysRevApplied.23.044018.pdf BibTex