Publications HAL de la collection CHIREX

Journal articles

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
Accès au bibtex
https://arxiv.org/pdf/2310.01623 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, 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
Accès au texte intégral et bibtex
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
Accès au texte intégral et bibtex
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
Accès au texte intégral et bibtex
https://hal.science/hal-04553207/file/add5751_ArticleContent_v15_FINAL_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
Accès au texte intégral et bibtex
https://hal.science/hal-04769717/file/SAF_Skyrmion_OAM_Willey_manuscript_28052024.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, ⟨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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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
Accès au texte intégral et bibtex
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
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
Accès au texte intégral et bibtex
https://hal.science/hal-04643875/file/Balan-PhysRevApplied.21.064023.pdf BibTex