305 results on '"Vogel, Jan"'
Search Results
2. Improving N\'eel domain walls dynamics and skyrmion stability using He ion irradiation
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Balan, Cristina, van der Jagt, Johannes W., Fassatoui, Aymen, Garcia, Jose Peña, Jeudy, Vincent, Thiaville, André, Vogel, Jan, Bonfim, Marlio, Ranno, Laurent, Ravelosona, Dafiné, and Pizzini, Stefania
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Condensed Matter - Materials Science - Abstract
Magnetization reversal and domain wall dynamics in Pt/Co/AlOx trilayers have been tuned by He+ ion irradiation. Fluences up to 1.5x10$^{15}$ ions/cm$^2$ strongly decrease the perpendicular magnetic anisotropy (PMA), without affecting neither the spontaneous magnetization nor the strength of the Dzyaloshinskii-Moriya interaction (DMI). This confirms the robustness of the DMI interaction against interfacial chemical intermixing, already predicted by theory. In parallel with the decrease of the PMA in the irradiated samples, a strong decrease of the depinning field is observed. This allows the domain walls to reach large maximum velocities with lower magnetic fields with respect to those needed for the pristine films. Decoupling PMA from DMI can therefore be beneficial for the design of low energy devices based on domain wall dynamics. When the samples are irradiated with larger He+ fluences, the magnetization gets close to the out-of-plane/in-plane reorientation transition where 100nm size magnetic skyrmions are stabilized. We observe that as the He+ fluence increases, the skyrmion size decreases while these magnetic textures become more stable against the application of an external magnetic field., Comment: 10 pages, 4 figures
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- 2023
3. Stability of the In-Plane Room Temperature van der Waals Ferromagnet Chromium Ditelluride and Its Conversion to Chromium-Interleaved CrTe$_2$ Compounds
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Purbawati, Anike, Sarkar, Suman, Pairis, Sébastien, Kostka, Marek, Hadj-Azzem, Abdellali, Dufeu, Didier, Singh, Priyank, Bourgault, Daniel, Nuñez-Regueiro, Manuel, Vogel, Jan, Renard, Julien, Marty, Laëtitia, Fabre, Florentin, Finco, Aurore, Jacques, Vincent, Ren, Lei, Tiwari, Vivekanand, Robert, Cedric, Marie, Xavier, Bendiab, Nedjma, Rougemaille, Nicolas, and Coraux, Johann
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Condensed Matter - Materials Science - Abstract
Van der Waals magnetic materials are building blocks for novel kinds of spintronic devices and playgrounds for exploring collective magnetic phenomena down to the two-dimensional limit. Chromium-tellurium compounds are relevant in this perspective. In particular, the 1$T$ phase of CrTe$_2$ has been argued to have a Curie temperature above 300~K, a rare and desirable property in the class of lamellar materials, making it a candidate for practical applications. However, recent literature reveals a strong variability in the reported properties, including magnetic ones. Using electron microscopy, diffraction and spectroscopy techniques, together with local and macroscopic magnetometry approaches, our work sheds new light on the structural, chemical and magnetic properties of bulk 1$T$-CrTe$_2$ exfoliated in the form of flakes having a thickness ranging from few to several tens of nanometers. We unambiguously establish that 1$T$-CrTe$_2$ flakes are ferromagnetic above room temperature, have an in-plane easy axis of magnetization, low coercivity, and we confirm that their Raman spectroscopy signatures are two modes, $E_{2\text{g}}$ (103.5~cm$^{-1}$) and $A_{1\text{g}}$ (136.5~cm$^{-1}$). We also prove that thermal annealing causes a phase transformation to monoclinic Cr$_5$Te$_8$ and, to a lesser extent, to trigonal Cr$_5$Te$_8$. In sharp contrast with 1$T$-CrTe$_2$, none of these compounds have a Curie temperature above room temperature, and they both have perpendicular magnetic anisotropy. Our findings reconcile the apparently conflicting reports in the literature and open opportunities for phase-engineered magnetic properties.
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- 2023
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4. Tuning the dynamics of chiral domain walls of ferrimagnetic films with the magneto-ionic effect
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Balan, Cristina, Garcia, Jose Pena, Fassatoui, Aymen, Vogel, Jan, Chaves, Dayane de Souza, Bonfim, Marlio, Rueff, Jean-Pascal, Ranno, Laurent, and Pizzini, Stefania
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Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
The manipulation of magnetism with a gate voltage is expected to lead the way towards the realization of energy-efficient spintronics devices and high-performance magnetic memories. Exploiting magneto-ionic effects under micro-patterned electrodes in solid-state devices adds the possibility to modify magnetic properties locally, in a non-volatile and reversible way. Tuning magnetic anisotropy, magnetization and Dzyaloshinskii-Moriya interaction allows modifying at will the dynamics of non trivial magnetic textures such as skyrmions and chiral domain walls in magnetic race tracks. In this work, we illustrate efficient magneto-ionic effects in a ferrimagnetic Pt/Co/Tb stack using a ZrO2 thin layer as a solid state ionic conductor. When a thin layer of terbium is deposited on top of cobalt, it acquires a magnetic moment that aligns antiparallel to that of cobalt, reducing the effective magnetization. Below the micro-patterned electrodes, the voltage-driven migration of oxygen ions in a ZrO2 towards the ferrimagnetic stack partially oxidizes the Tb layer, leading to the local variation not only of the spontaneous magnetization, but also of the effective magnetic anisotropy and of the Dzyaloshinskii-Moriya interaction. This leads to a huge increase of the domain wall velocity, which varies from 10 m/s in the pristine state to 250 m/s after gating. This non-volatile and reversible tuning of the domain wall dynamics may lead to applications to reprogrammable magnetic memories or other spintronic devices., Comment: 11 pages, 7 figures
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- 2022
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5. Improvement of magnetic domain wall dynamics by buffer layer annealing of Pt/Co/Pt
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Pakam, Tchilabalo, Adanlété Adjanoh, Assiongbon, Afenyiveh, Serge Dzo Mawuefa, Ranno, Laurent, Vogel, Jan, and Pizzini, Stefania
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- 2024
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6. Current-driven domain wall dynamics in ferrimagnetic Ni-doped Mn4N films : very large domain wall velocities and reversal of motion direction across the magnetic compensation point
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Ghosh, Sambit, Komori, Taro, Hallal, Ali, Garcia, Jose Peña, Gushi, Toshiki, Hirose, Taku, Mitarai, Haruka, Okuno, Hanako, Vogel, Jan, Chshiev, Mairbek, Attané, Jean-Philippe, Vila, Laurent, Suemasu, Takashi, and Pizzini, Stefania
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Condensed Matter - Materials Science ,Condensed Matter - Other Condensed Matter - Abstract
Spin-transfer torque (STT) and spin-orbit torque (SOT) are spintronic phenomena allowing magnetization manipulation using electrical currents. Beyond their fundamental interest, they allow developing new classes of magnetic memories and logic devices, in particular based on domain wall (DW) motion. In this work, we report the study of STT driven DW motion in ferrimagnetic manganese nickel nitride (Mn4-xNixN) films, in which a fine adjustment of the Ni content allows setting the magnetic compensation at room temperature. The reduced magnetization, combined with the large spin polarization of conduction electrons, strongly enhances the STT so that domain wall velocities approaching 3000 m/s can be obtained for Ni compositions close to the compensation point. In addition, a reversal of the domain wall motion direction is observed when the magnetic compensation composition is crossed. This striking feature, related to the change of direction of the spin polarization with respect to that of the net magnetization, is clarified by ab initio band structure calculations., Comment: 24 pages, 4 figures
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- 2021
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7. Anisotropic skyrmion bubbles in ultra-thin epitaxial Au$_{0.67}$Pt$_{0.33}$/Co/W films
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Camosi, Lorenzo, Peña-Garcia, José, Fruchart, Olivier, Pizzini, Stefania, Locatelli, Andrea, Menteş, Tevfik Onur, Genuzio, Francesca, Shaw, Justin, Nembach, Hans, and Vogel, Jan
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Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We studied the symmetry of magnetic properties and the resulting magnetic textures in ultra-thin epitaxial Au$_{0.67}$Pt$_{0.33}$/Co/W, a model system exhibiting perpendicular magnetic anisotropy and interface Dzyaloshinskii-Moriya interaction (DMI). As a peculiar feature, the C$_\mathrm{2v}$ crystal symmetry induced by the Co/W interface results in an additional uniaxial in-plane magnetic anisotropy in the cobalt layer. Photoemission electron microscopy with magnetic sensitivity reveals the formation of self-organized magnetic stripe domains oriented parallel to the hard in-plane magnetization axis. We attribute this behavior to the lower domain wall energy when oriented along this axis, where both the DMI and the in-plane magnetic anisotropy favor a N\'{e}el domain wall configuration. The anisotropic domain wall energy also leads to the formation of elliptical skyrmion bubbles in a weak out-of-plane magnetic field.
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- 2020
8. Reversible vs. irreversible voltage manipulation of interfacial magnetic anisotropy in Pt/Co/oxide multilayers
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Fassatoui, Aymen, Garcia, Jose Pena, Vogel, Jan, Ranno, Laurent, Bernand-Mantel, Anne, Béa, Hélène, Pizzini, Sergio, and Pizzini, Stefania
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
The perpendicular magnetic anisotropy at the Co/oxide interface in Pt/Co/MOx (MOx = MgOx, AlOx, TbOx) was modified by an electric field using a 10 nm-thick ZrO2 as a solid electrolyte. The large voltage-driven modification of interfacial magnetic anisotropy and the non-volatility of the effect is explained in terms of the migration of oxygen ions towards/away from the Co/MOx interface. While the effect is reversible in Pt/Co/AlOx and Pt/Co/TbOx, where the Co layer can be oxidised or reduced, in Pt/Co/MgOx the effect has been found to be irreversible. We propose that these differences may be related to the different nature of the ionic conduction within the MOx layers., Comment: Main texte (3 figures) + supplemental Information (3 figures)
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- 2020
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9. In-plane magnetic domains and N\'eel-like domain walls in thin flakes of the room temperature CrTe$_2$ van der Waals ferromagnet
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Purbawati, Anike, Coraux, Johann, Vogel, Jan, Hadj-Azzem, Abdellali, Wu, NianJheng, Bendiab, Nedjma, Jégouso, David, Renard, Julien, Marty, Laetitia, Bouchiat, Vincent, Sulpice, André, Aballe, Lucia, Foerster, Michael, Genuzio, Francesca, Locatelli, Andrea, Menteş, Tevfik Onur, Han, Zheng Vitto, Sun, Xingdan, Núñez-Regueiro, Manuel, and Rougemaille, Nicolas
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Condensed Matter - Materials Science - Abstract
The recent discovery of magnetic van der Waals materials has triggered a wealth of investigations in materials science, and now offers genuinely new prospects for both fundamental and applied research. Although the catalogue of van der Waals ferromagnets is rapidly expanding, most of them have a Curie temperature below 300 K, a notable disadvantage for potential applications. Combining element-selective x-ray magnetic imaging and magnetic force microscopy, we resolve at room temperature the magnetic domains and domains walls in micron-sized flakes of the CrTe$_2$ van der Waals ferromagnet. Flux-closure magnetic patterns suggesting in-plane six-fold symmetry are observed. Upon annealing the material above its Curie point (315 K), the magnetic domains disappear. By cooling back down the sample, a different magnetic domain distribution is obtained, indicating material stability and lack of magnetic memory upon thermal cycling. The domain walls presumably have N\'eel texture, are preferentially oriented along directions separated by 120 degrees, and have a width of several tens of nanometers. Besides microscopic mapping of magnetic domains and domain walls, the coercivity of the material is found to be of a few mT only, showing that the CrTe$_2$ compound is magnetically soft. The coercivity is found to increase as the volume of the material decreases.
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- 2020
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10. Current-Driven Skyrmion Dynamics and Drive-Dependent Skyrmion Hall Effect in an Ultrathin Film
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Juge, Roméo, Je, Soong-Geun, Chaves, Dayane de Souza, Buda-Prejbeanu, Liliana D., Peña-Garcia, José, Nath, Jayshankar, Miron, Ioan Mihai, Rana, Kumari Gaurav, Aballe, Lucia, Foerster, Michael, Genuzio, Francesca, Menteş, Tevfik Onur, Locatelli, Andrea, Maccherozzi, Francesco, Dhesi, Sarnjeet S., Belmeguenai, Mohamed, Roussigné, Yves, Auffret, Stéphane, Pizzini, Stefania, Gaudin, Gilles, Vogel, Jan, and Boulle, Olivier
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Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Materials Science - Abstract
Magnetic skyrmions are chiral spin textures that hold great promise as nanoscale information carriers. Since their first observation at room temperature, progress has been made in their current-induced manipulation, with fast motion reported in stray-field-coupled multilayers. However, the complex spin textures with hybrid chiralities and large power dissipation in these multilayers limit their practical implementation and the fundamental understanding of their dynamics. Here, we report on the current-driven motion of N\'eel skyrmions with diameters in the 100-nm range in an ultrathin Pt/Co/MgO trilayer. We find that these skyrmions can be driven at a speed of 100 m/s and exhibit a drive-dependent skyrmion Hall effect, which is accounted for by the effect of pinning. Our experiments are well substantiated by an analytical model of the skyrmion dynamics as well as by micromagnetic simulations including material inhomogeneities. This good agreement is enabled by the simple skyrmion spin structure in our system and a thorough characterization of its static and dynamical properties., Comment: 9 pages, 4 figures + Supplementary Information (12 pages, 9 figures)
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- 2019
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11. Using hard-x-ray photoelectron spectroscopy to measure the oxidation state of gated Co / AlOx interfaces
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Balan, Cristina, primary, Fischer, Johanna, additional, Gueneau, Capucine, additional, Fassatoui, Aymen, additional, Rueff, Jean-Pascal, additional, Ceolin, Denis, additional, De-Santis, Maurizio, additional, Vogel, Jan, additional, Ranno, Laurent, additional, Béa, Hélène, additional, and Pizzini, Stefania, additional
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- 2024
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12. Millimeter-sized magnetic domains in perpendicularly magnetized ferrimagnetic Mn4N thin films grown on SrTiO3
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Gushi, Toshiki, Vila, Laurent, Fruchart, Olivier, Marty, Alain, Pizzini, Stefania, Vogel, Jan, Takata, Fumiya, Anzai, Akihito, Toko, Kaoru, Suemasu, Takashi, and Attané, Jean-Philippe
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Condensed Matter - Materials Science - Abstract
The use of epitaxial layers for domain wall-based spintronic applications is often hampered by the presence of pinning sites. Here, we show that when depositing Mn4N(10 nm) epitaxial films, the replacement of MgO(001) by SrTiO3(001) substrates allows minimizing the misfit, and to obtain an improved crystalline quality, a sharper switching, a full remanence, a high anisotropy and remarkable millimeter-sized magnetic domains, with straight and smooth domain walls. In a context of rising interest for current-induced domain wall motion in rare
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- 2018
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13. Velocity enhancement by synchronization of magnetic domain walls
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Hrabec, Aleš, Křižáková, Viola, Pizzini, Stefania, Sampaio, João, Thiaville, André, Rohart, Stanislas, and Vogel, Jan
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Magnetic domain walls are objects whose dynamics is inseparably connected to their structure. In this work we investigate magnetic bilayers, which are engineered such that a coupled pair of domain walls, one in each layer, is stabilized by a cooperation of Dzyaloshinskii-Moriya interaction and flux-closing mechanism. The dipolar field mediating the interaction between the two domain walls, links not only their position but also their structure. We show that this link has a direct impact on their magnetic field induced dynamics. We demonstrate that in such a system the coupling leads to an increased domain wall velocity with respect to single domain walls. Since the domain wall dynamics is observed in a precessional regime, the dynamics involves the synchronization between the two walls, to preserve the flux closure during motion. Properties of these coupled oscillating walls can be tuned by an additional in-plane magnetic field enabling a rich variety of states, from perfect synchronization to complete detuning.
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- 2018
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14. Unravelling Dzyaloshinskii-Moriya interaction and chiral nature of Graphene/Cobalt interface
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Ajejas, Fernando, Gudín, Adrian, Guerrero, Ruben, Niño, Miguel Angel, Pizzini, Stefania, Vogel, Jan, Valvidares, Manuel, Gargiani, Pierluigi, Cabero, Mariona, Varela, Maria, Camarero, Julio, Miranda, Rodolfo, and Perna, Paolo
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Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
A major challenge for future spintronics is to develop suitable spin transport channels with long spin lifetime and propagation length. Graphene can meet these requirements, even at room temperature. On the other side, taking advantage of the fast motion of chiral textures, i.e., N\'eel-type domain walls and magnetic skyrmions, can satisfy the demands for high-density data storage, low power consumption and high processing speed. We have engineered epitaxial structures where an epitaxial ferromagnetic Co layer is sandwiched between an epitaxial Pt(111) buffer grown in turn onto MgO(111) substrates and a graphene layer. We provide evidence of a graphene-induced enhancement of the perpendicular magnetic anisotropy up to 4 nm thick Co films, and of the existence of chiral left-handed N\'eel-type domain walls stabilized by the effective Dzyaloshinskii-Moriya interaction (DMI) in the stack. The experiments show evidence of a sizeable DMI at the gr/Co interface, which is described in terms of a conduction electron mediated Rashba-DMI mechanism and points opposite to the Spin Orbit Coupling-induced DMI at the Co/Pt interface. In addition, the presence of graphene results in: i) a surfactant action for the Co growth, producing an intercalated, flat, highly perfect fcc film, pseudomorphic with Pt and ii) an efficient protection from oxidation. The magnetic chiral texture is stable at room temperature and grown on insulating substrate. Our findings open new routes to control chiral spin structures using interfacial engineering in graphene-based systems for future spin-orbitronics devices fully integrated on oxide substrates., Comment: 10 pages, 6 figures
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- 2018
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15. Discovery of chromene compounds as inhibitors of PvdQ acylase of Pseudomonas aeruginosa
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Vogel, Jan G.T., Wibowo, Joko P., Fan, Hillina, Setroikromo, Rita, Wang, Kan, Dömling, Alexander, Dekker, Frank J., and Quax, Wim J.
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- 2022
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16. Micromagnetics of anti-skyrmions in ultrathin films
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Camosi, Lorenzo, Rougemaille, Nicolas, Fruchart, Olivier, Vogel, Jan, and Rohart, Stanislas
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Condensed Matter - Materials Science ,Condensed Matter - Other Condensed Matter - Abstract
We present a combined analytical and numerical micromagnetic study of the equilibrium energy, size and shape of anti-skyrmionic magnetic configurations. Anti-skyrmions can be stabilized when the Dzyaloshinskii-Moriya interaction has opposite signs along two orthogonal in-plane directions, breaking the magnetic circular symmetry. We compare the equilibrium energy, size and shape of anti-skyrmions and skyrmions that are stabilized respectively in environments with anisotropic and isotropic Dzyaloshinskii-Moriya interaction, but with the same strength of the magnetic interactions.When the dipolar interactions are neglected the skyrmion and the anti-skyrmion have the same energy, shape and size in their respective environment. However, when dipolar interactions are considered, the energy of the anti-skyrmion is strongly reduced and its equilibrium size increased with respect to the skyrmion. While the skyrmion configuration shows homochiral N\'{e}el magnetization rotations, anti-skyrmions show partly N\'{e}el and partly Bloch rotations. The latter do not produce magnetic charges and thus cost less dipolar energy. Both magnetic configurations are stable when the magnetic energies almost cancel each other, which means that a small variation of one parameter can drastically change their configuration, size and energy., Comment: Published as Physical Review B 97, 134404 (2018)
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- 2017
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17. Fighting Acinetobacter baumannii infections with the acylase PvdQ
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Vogel, Jan, Jansen, Lisa, Setroikromo, Rita, Cavallo, Francis M., van Dijl, Jan Maarten, and Quax, Wim J.
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- 2022
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18. A whole genome sequencing study of moderate to severe asthma identifies a lung function locus associated with asthma risk
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Chang, Diana, Hunkapiller, Julie, Bhangale, Tushar, Reeder, Jens, Mukhyala, Kiran, Tom, Jennifer, Cowgill, Amy, Vogel, Jan, Forrest, William F., Khan, Zia, Stockwell, Amy, McCarthy, Mark I., Staton, Tracy L., Olsson, Julie, Holweg, Cecile T. J., Cheung, Dorothy S., Chen, Hubert, Brauer, Matthew J., Graham, Robert R., Behrens, Timothy, Wilson, Mark S., Arron, Joseph R., Choy, David F., and Yaspan, Brian L.
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- 2022
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19. Tuning domain wall velocity with Dzyaloshinskii-Moriya interaction
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Ajejas, Fernando, Krizakova, Viola, Chaves, Dayane de Souza, Vogel, Jan, Perna, Paolo, Guerrero, Ruben, Gudin, Adrian, Camarero, Julio, and Pizzini, Stefania
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Condensed Matter - Materials Science - Abstract
We have studied a series of Pt/Co/M epitaxial trilayers, in which Co is sandwiched between Pt and a non magnetic layer M (Pt, Ir, Cu, Al). Using polar magneto-optical Kerr microscopy, we show that the field- induced domain wall speeds are strongly dependent on the nature of the top layer, they increase going from M=Pt to lighter top metallic overlayers, and can reach several 100 m/s for Pt/Co/Al. The DW dynamics is consistent with the presence of chiral N\'eel walls stabilized by interfacial Dzyaloshinskii-Moriya interaction (DMI) whose strength increases going from Pt to Al top layers. This is explained by the presence of DMI with opposite sign at the Pt/Co and Co/M interfaces, the latter increasing in strength going towards heavier atoms, possibly due to the increasing spin-orbit interaction. This work shows that in non-centrosymmetric trilayers the domain wall dynamics can be finely tuned by engineering the DMI strength, in view of efficient devices for logic and spitronics applications., Comment: 5 pages, 4 Figures
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- 2017
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20. Dependence of Dzyaloshinskii-Moriya interaction on the oxygen coverage in Pt/Co/MOx trilayers
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Chaves, Dayane de Souza, Ajejas, Fernando, Krizakova, Viola, Vogel, Jan, and Pizzini, Stefania
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Condensed Matter - Materials Science - Abstract
We have studied the interfacial Dzyaloshinskii-Moriya interaction (DMI) in a series of Pt/Co/MOx (M=Al, Gd) trilayers in which the degree of oxidation of the top Co interface is varied. To access to reliable values of the DMI strength, we have used a method based on the measurement of the saturation velocity of field driven chiral N\'eel domain walls. We show that the effective DMI strength in the Pt/Co/MOx trilayers varies with the oxidation degree of the Co/MOx interface. This strongly suggests that the Co/MOx interface gives a distinct contribution to the total DMI, adding to that of the Pt/Co interface. The DMI presents a maximum for the oxygen coverage maximizing also the interface magnetic anisotropy energy Ks. This calls for common microscopic origins for the contributions of the Co/MOx interface to DMI and Ks., Comment: 6 pages, 4 Figures
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- 2017
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21. Magnetic skyrmions in confined geometries : effect of the magnetic field and the disorder
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Juge, Roméo, Je, Soong-Geun, Chaves, Dayane de Souza, Pizzini, Stefania, Buda-Prejbeanu, Liliana D., Aballe, Lucia, Foerster, Michael, Locatelli, Andrea, Menteş, Tevfik Onur, Sala, Alessandro, Maccherozzi, Francesco, Dhesi, Sarnjeet S., Auffret, Stéphane, Gaudin, Gilles, Vogel, Jan, and Boulle, Olivier
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We report on the effect of the lateral confinement and a perpendicular magnetic field on isolated room-temperature magnetic skyrmions in sputtered Pt/Co/MgO nanotracks and nanodots. We show that the skyrmions size can be easily tuned by playing on the lateral dimensions of the nanostructures and by using external magnetic field amplitudes of a few mT, which allow to reach sub-100 nm diameters. Our XMCD-PEEM observations also highlight the important role of the pinning on the skyrmions size and stability under an out-of-plane magnetic field. Micromagnetic simulations reveal that the effect of local pinning can be well accounted for by considering the thin film grain structure with local anisotropy variations and reproduce well the dependence of the skyrmion diameter on the magnetic field and the geometry., Comment: 17 pages, 4 figures
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- 2017
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22. Anisotropic Dzyaloshinskii-Moriya Interaction in ultra-thin epitaxial Au/Co/W(110)
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Camosi, Lorenzo, Rohart, Stanislas, Fruchart, Olivier, Pizzini, Stefania, Belmeguenai, Mohamed, Roussigné, Yves, Stachkevitch, Andreï, Chérif, Salim Mourad, Ranno, Laurent, De Santis, Maurizio, and Vogel, Jan
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Condensed Matter - Materials Science ,Condensed Matter - Other Condensed Matter - Abstract
We have used Brillouin Light Scattering spectroscopy to independently determine the in-plane Magneto-Crystalline Anisotropy and the Dzyaloshinskii-Moriya Interaction (DMI) in out-of-plane magnetized Au/Co/W(110). We found that the DMI strength is 2-3 times larger along the bcc$[\bar{1}10]$ than along the bcc$[001]$ direction. We use analytical considerations to illustrate the relationship between the crystal symmetry of the stack and the anisotropy of microscopic DMI. Such an anisotropic DMI is the first step to realize isolated elliptical skyrmions or anti-skyrmions in thin film systems with $C_{2v}$ symmetry., Comment: Revised and extended version
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- 2017
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23. Analysis of protein-altering variants in telomerase genes and their association with MUC5B common variant status in patients with idiopathic pulmonary fibrosis: a candidate gene sequencing study
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Dressen, Amy, Abbas, Alexander R, Cabanski, Christopher, Reeder, Janina, Ramalingam, Thirumalai R, Neighbors, Margaret, Bhangale, Tushar R, Brauer, Matthew J, Hunkapiller, Julie, Reeder, Jens, Mukhyala, Kiran, Cuenco, Karen, Tom, Jennifer, Cowgill, Amy, Vogel, Jan, Forrest, William F, Collard, Harold R, Wolters, Paul J, Kropski, Jonathan A, Lancaster, Lisa H, Blackwell, Timothy S, Arron, Joseph R, and Yaspan, Brian L
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Biomedical and Clinical Sciences ,Cardiovascular Medicine and Haematology ,Clinical Sciences ,Rare Diseases ,Genetics ,Lung ,Clinical Trials and Supportive Activities ,Clinical Research ,Autoimmune Disease ,2.1 Biological and endogenous factors ,Aetiology ,Respiratory ,Aged ,Case-Control Studies ,Clinical Trials as Topic ,Female ,Humans ,Idiopathic Pulmonary Fibrosis ,Male ,Middle Aged ,Mucin-5B ,Telomere Homeostasis ,Whole Genome Sequencing ,Public Health and Health Services ,Other Medical and Health Sciences ,Cardiovascular medicine and haematology ,Clinical sciences - Abstract
BackgroundIdiopathic pulmonary fibrosis (IPF) risk has a strong genetic component. Studies have implicated variations at several loci, including TERT, surfactant genes, and a single nucleotide polymorphism at chr11p15 (rs35705950) in the intergenic region between TOLLIP and MUC5B. Patients with IPF who have risk alleles at rs35705950 have longer survival from the time of IPF diagnosis than do patients homozygous for the non-risk allele, whereas patients with shorter telomeres have shorter survival times. We aimed to assess whether rare protein-altering variants in genes regulating telomere length are enriched in patients with IPF homozygous for the non-risk alleles at rs35705950.MethodsBetween Nov 1, 2014, and Nov 1, 2016, we assessed blood samples from patients aged 40 years or older and of European ancestry with sporadic IPF from three international phase 3 clinical trials (INSPIRE, CAPACITY, ASCEND), one phase 2 study (RIFF), and US-based observational studies (Vanderbilt Clinical Interstitial Lung Disease Registry and the UCSF Interstitial Lung Disease Clinic registry cohorts) at the Broad Institute (Cambridge, MA, USA) and Human Longevity (San Diego, CA, USA). We also assessed blood samples from non-IPF controls in several clinical trials. We did whole-genome sequencing to assess telomere length and identify rare protein-altering variants, stratified by rs35705950 genotype. We also assessed rare functional variation in TERT exons and compared telomere length and disease progression across genotypes.FindingsWe assessed samples from 1510 patients with IPF and 1874 non-IPF controls. 30 (3%) of 1046 patients with an rs35705950 risk allele had a rare protein-altering variant in TERT compared with 34 (7%) of 464 non-risk allele carriers (odds ratio 0·40 [95% CI 0·24-0·66], p=0·00039). Subsequent analyses identified enrichment of rare protein-altering variants in PARN and RTEL1, and rare variation in TERC in patients with IPF compared with controls. We expanded our study population to provide a more accurate estimation of rare variant frequency in these four loci, and to calculate telomere length. The proportion of patients with at least one rare variant in TERT, PARN, TERC, or RTEL1 was higher in patients with IPF than in controls (149 [9%] of 1739 patients vs 205 [2%] of 8645 controls, p=2·44 × 10-8). Patients with IPF who had a variant in any of the four identified telomerase component genes had telomeres that were 3·69-16·10% shorter than patients without a variant in any of the four genes and had an earlier mean age of disease onset than patients without one or more variants (65·1 years [SD 7·8] vs 67·1 years [7·9], p=0·004). In the placebo arms of clinical trials, shorter telomeres were significantly associated with faster disease progression (1·7% predicted forced vital capacity per kb per year, p=0·002). Pirfenidone had treatment benefit regardless of telomere length (p=4·24 × 10-8 for telomere length lower than the median, p=0·0044 for telomere length greater than the median).InterpretationRare protein-altering variants in TERT, PARN, TERC, and RTEL1 are enriched in patients with IPF compared with controls, and, in the case of TERT, particularly in individuals without a risk allele at the rs35705950 locus. This suggests that multiple genetic factors contribute to sporadic IPF, which might implicate distinct mechanisms of pathogenesis and disease progression.FundingGenentech, National Institutes of Health, Francis Family Foundation, Pulmonary Fibrosis Foundation, Nina Ireland Program for Lung Health, US Department of Veterans Affairs.
- Published
- 2018
24. Room temperature chiral magnetic skyrmion in ultrathin magnetic nanostructures
- Author
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Boulle, Olivier, Vogel, Jan, Yang, Hongxin, Pizzini, Stefania, Chaves, Dayane de Souza, Locatelli, Andrea, Sala, Tevfik Onur Menteş Alessandro, Buda-Prejbeanu, Liliana D., Klein, Olivier, Belmeguenai, Mohamed, Roussigné, Yves, Stashkevich, Andrey, Chérif, Salim Mourad, Aballe, Lucia, Foerster, Michael, Chshiev, Mairbek, Auffret, Stéphane, Miron, Ioan Mihai, and Gaudin, Gilles
- Subjects
Condensed Matter - Materials Science - Abstract
Magnetic skyrmions are chiral spin structures with a whirling configuration. Their topological properties, nanometer size and the fact that they can be moved by small current densities have opened a new paradigm for the manipulation of magnetisation at the nanoscale. To date, chiral skyrmion structures have been experimentally demonstrated only in bulk materials and in epitaxial ultrathin films and under external magnetic field or at low temperature. Here, we report on the observation of stable skyrmions in sputtered ultrathin Pt/Co/MgO nanostructures, at room temperature and zero applied magnetic field. We use high lateral resolution X-ray magnetic circular dichroism microscopy to image their chiral N\'eel internal structure which we explain as due to the large strength of the Dzyaloshinskii-Moriya interaction as revealed by spin wave spectroscopy measurements. Our results are substantiated by micromagnetic simulations and numerical models, which allow the identification of the physical mechanisms governing the size and stability of the skyrmions., Comment: Submitted version. Extended version to appear in Nature Nanotechnology
- Published
- 2016
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25. Chirality-induced asymmetric magnetic nucleation in Pt/Co/AlOx ultrathin microstructures
- Author
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Pizzini, Stefania, Vogel, Jan, Rohart, Stanislas, Buda, Liliana-Daniela, Jué, E., Boulle, Olivier, Miron, Ioan Mihai, Safeer, C. K., Auffret, Stéphane, Gaudin, Gilles, and Thiaville, André
- Subjects
Condensed Matter - Materials Science - Abstract
The nucleation of reversed magnetic domains in Pt/Co/AlO$_{x}$ microstructures with perpendicular anisotropy was studied experimentally in the presence of an in-plane magnetic field. For large enough in-plane field, nucleation was observed preferentially at an edge of the sample normal to this field. The position at which nucleation takes place was observed to depend in a chiral way on the initial magnetization and applied field directions. An explanation of these results is proposed, based on the existence of a sizable Dzyaloshinskii-Moriya interaction in this sample. Another consequence of this interaction is that the energy of domain walls can become negative for in-plane fields smaller than the effective anisotropy field., Comment: Published version, Physical Review Letters 113, 047203 (2014)
- Published
- 2014
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26. Manipulating domain wall chirality by current pulses in Permalloy/Ir nanostrips
- Author
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Ishaque, Zahid, Nguyen, Van Dai, Fruchart, Olivier, Pizzini, Stefania, Rougemaille, Nicolas, Perl, Svenja, Toussaint, Jean-Christophe, and Vogel, Jan
- Subjects
Condensed Matter - Materials Science - Abstract
Using magnetic force microscopy and micromagnetic simulations, we studied the effect of Oersted magnetic fields on the chirality of transverse magnetic domain walls in Fe$_{20}$Ni$_{80}$/Ir bilayer nanostrips. Applying nanosecond current pulses with a current density of around $2\times10^{12}$ A/m$^2$, the chirality of a transverse domain wall could be switched reversibly and reproducibly. These current densities are similar to the ones used for current-induced domain wall motion, indicating that the Oersted field may stabilize the transverse wall chirality during current pulses and prevent domain wall transformations.
- Published
- 2013
27. Direct Observation of Massless Domain Wall Dynamics in Nanostripes with Perpendicular Magnetic Anisotropy
- Author
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Vogel, Jan, Bonfim, Marlio, Rougemaille, Nicolas, Boulle, Olivier, Miron, Ioan Mihai, Auffret, Stéphane, Rodmacq, Bernard, Gaudin, Gilles, Cezar, J. C., Sirotti, Fausto, and Pizzini, Stefania
- Subjects
Condensed Matter - Materials Science - Abstract
Domain wall motion induced by nanosecond current pulses in nanostripes with perpendicular magnetic anisotropy (Pt/Co/AlO$_x$) is shown to exhibit negligible inertia. Time-resolved magnetic microscopy during current pulses reveals that the domain walls start moving, with a constant speed, as soon as the current reaches a constant amplitude, and no or little motion takes place after the end of the pulse. The very low 'mass' of these domain walls is attributed to the combination of their narrow width and high damping parameter $\alpha$. Such a small inertia should allow accurate control of domain wall motion, by tuning the duration and amplitude of the current pulses.
- Published
- 2012
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28. Phase diagram of magnetic domain walls in spin valve nano-stripes
- Author
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Rougemaille, Nicolas, Uhlîr, Vojtech, Fruchart, Olivier, Pizzini, Stefania, Vogel, Jan, and Toussaint, Jean-Christophe
- Subjects
Condensed Matter - Materials Science - Abstract
We investigate numerically the transverse versus vortex phase diagram of head-to-head domain walls in Co/Cu/Py spin valve nano-stripes (Py: Permalloy), in which the Co layer is mostly single domain while the Py layer hosts the domain wall. The range of stability of the transverse wall is shifted towards larger thickness compared to single Py layers, due to a magnetostatic screening effect between the two layers. An approached analytical scaling law is derived, which reproduces faithfully the phase diagram., Comment: 4 pages
- Published
- 2012
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29. Perpendicular anisotropy of ultrathin epitaxial cobalt films on graphene
- Author
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Vo-Van, Chi, Kassir-Bodon, Zoukaa, Yang, Hongxing, Coraux, Johann, Vogel, Jan, Pizzini, Stefania, Bayle-Guillemaud, Pascale, Chshiev, Mairbek, Ranno, Laurent, Santonacci, Valérie, David, Philippe, Salvador, Violaine, and Fruchart, Olivier
- Subjects
Condensed Matter - Materials Science - Abstract
Graphene is attractive for spintronics due to its long spin life time and high mobility. So far only thick and polycrystalline slabs have been used as ferromagnetic electrodes. We report the growth of flat, epitaxial ultrathin Co films on graphene. These display perpendicular magnetic anisotropy in the thickness range 0.5-1nm, which is confirmed by theory. PMA, epitaxy and ultrathin thickness bring new perspectives for graphene-based spintronic devices such as the zero-field control of an arbitrary magnetization direction, band matching between electrodes and graphene, and interface effects such as Rashba and electric field control of magnetism.
- Published
- 2010
30. Direct observation of Oersted-field-induced magnetization dynamics in magnetic nanostripes
- Author
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Uhlîr, Vojtech, Pizzini, Stefania, Rougemaille, Nicolas, Cros, Vincent, Jimenez, Erika, Ranno, Laurent, Fruchart, Olivier, Urbanek, Michal, Gaudin, Gilles, Camarero, Julio, Tieg, Carsten, Sirotti, Fausto, Wagner, Edouard, and Vogel, Jan
- Subjects
Condensed Matter - Materials Science - Abstract
We have used time-resolved x-ray photoemission electron microscopy to investigate the magnetization dynamics induced by nanosecond current pulses in NiFe/Cu/Co nanostripes. A large tilt of the NiFe magnetization in the direction transverse to the stripe is observed during the pulses. We show that this effect cannot be quantitatively understood from the amplitude of the Oersted field and the shape anisotropy. High frequency oscillations observed at the onset of the pulses are attributed to precessional motion of the NiFe magnetization about the effective field. We discuss the possible origins of the large magnetization tilt and the potential implications of the static and dynamic effects of the Oersted field on current-induced domain wall motion in such stripes., Comment: Published in Phys. Rev. B 83, 020406 (2011) (Rapid Communications)
- Published
- 2010
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31. Anisotropic creep velocity of Dzyaloshinskii domain walls.
- Author
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Pakam, Tchilabalo, Adjanoh, Assiongbon Adanlété, Afenyiveh, Serge Dzo Mawuefa, Vogel, Jan, Pizzini, Stefania, and Ranno, Laurent
- Subjects
PERPENDICULAR magnetic anisotropy ,MAGNETIC films ,VELOCITY ,CREEP (Materials) - Abstract
We have measured the field-driven velocity of chiral Néel domain walls (DWs) stabilized by the Dzyaloshinskii–Moriya interaction (DMI) in a Pt/Co/Ta/Pt film with perpendicular magnetic anisotropy. A simple model based on the universal creep theory allows us to describe the anisotropic propagation of a DW along the contour of a bubble domain, driven by an out-of-plane field in the presence of a static in-plane field. This model is used to obtain the DMI constant from the measurement of the DW propagation with only one value of the in-plane field, simplifying the existing method relying on several measurements. The DMI constant extracted from the model is in good agreement with independent measurements. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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32. High domain wall velocity at zero magnetic field induced by low current densities in spin-valve nanostripes
- Author
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Pizzini, Stefania, Uhlir, Vojtech, Vogel, Jan, Rougemaille, Nicolas, Laribi, Sana, Cros, Vincent, Jimenez, Erika, Camarero, Julio, Tieg, Carsten, Bonet, Edgar, Bonfim, Marlio, Mattana, Richard, Deranlot, Cyrile, Petroff, Frédric, Ulysse, Christian, Faini, Giancarlo, and Fert, Albert
- Subjects
Condensed Matter - Materials Science - Abstract
Current-induced magnetic domain wall motion at zero magnetic field is observed in the permalloy layer of a spin-valve-based nanostripe using photoemission electron microscopy. The domain wall movement is hampered by pinning sites, but in between them high domain wall velocities (exceeding 150 m/s) are obtained for current densities well below $10^{12} \unit{A/m^2}$, suggesting that these trilayer systems are promising for applications in domain wall devices in case of well controlled pinning positions. Vertical spin currents in these structures provide a potential explanation for the increase in domain wall velocity at low current densities., Comment: Published version, Applied Physics Express 2, 023003 (2009) http://dx.doi.org/10.1143/APEX.2.023003
- Published
- 2008
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33. Analysis of anisotropy crossover due to oxygen in Pt/Co/MOx trilayer
- Author
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Manchon, Aurélien, Ducruet, Clarisse, Lombard, Lucien, Auffret, Stéphane, Rodmacq, Bernard, Dieny, Bernard, Pizzini, Stefania, Vogel, Jan, Uhlir, Vojtech, Hochstrasser, Michael, and Panaccione, Giancarlo
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Materials Science - Abstract
Extraordinary Hall effect and X-ray spectroscopy measurements have been performed on a series of Pt/Co/MOx trilayers (M=Al, Mg, Ta...) in order to investigate the role of oxidation in the onset of perpendicular magnetic anisotropy at the Co/MOx interface. It is observed that varying the oxidation time modifies the magnetic properties of the Co layer, inducing a magnetic anisotropy crossover from in-plane to out-of-plane. We focused on the influence of plasma oxidation on Pt/Co/AlOx perpendicular magnetic anisotropy. The interfacial electronic structure is analyzed via X-ray photoelectron spectroscopy measurements. It is shown that the maximum of out-of-plane magnetic anisotropy corresponds to the appearance of a significant density of Co-O bondings at the Co/AlOx interface.
- Published
- 2007
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34. X-Ray Analysis of Oxygen-induced Perpendicular Magnetic Anisotropy in Pt/Co/AlOx trilayer
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Manchon, Aurélien, Pizzini, Stefania, Vogel, Jan, Uhlir, Vojteh, Lombard, Lucien, Ducruet, Clarisse, Auffret, Stéphane, Rodmacq, Bernard, Dieny, Bernard, Hochstrasser, Michael, and Panaccione, Giancarlo
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Materials Science - Abstract
X-ray spectroscopy measurements have been performed on a series of Pt/Co/AlOx trilayers to investigate the role of Co oxidation in the perpendicular magnetic anisotropy of the Co/AlOx interface. It is observed that high temperature annealing modifies the magnetic properties of the Co layer, inducing an enhancement of the perpendicular magnetic anisotropy. The microscopic structural properties are analyzed via X-ray Absorption Spectroscopy, X-ray Magnetic Circular Dichroism and X-ray Photoelectron Spectroscopy measurements. It is shown that annealing enhances the amount of interfacial oxide, which may be at the origin of a strong perpendicular magnetic anisotropy.
- Published
- 2007
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- View/download PDF
35. Layer-resolved imaging of domain wall interactions in magnetic tunnel junction-like trilayers
- Author
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Vogel, Jan, Cherifi, Salia, Pizzini, Stefania, Romanens, Fabien, Camarero, Julio, Petroff, Frédéric, Heun, Stefan, and Locatelli, Andrea
- Subjects
Condensed Matter - Other Condensed Matter - Abstract
We have performed a layer-resolved, microscopic study of interactions between domain walls in two magnetic layers separated by a non-magnetic one, using high-resolution x-ray photoemission electron microscopy. Domain walls in the hard magnetic Co layer of a Co/Al2O3/FeNi trilayer with in-plane uniaxial anisotropy strongly modify the local magnetization direction in the soft magnetic FeNi layer. The stray fields associated to the domain walls lead to an antiparallel coupling between the local Co and FeNi moments. For domain walls parallel to the easy magnetization axis this interaction is limited to the domain wall region itself. For strongly charged (head-on or tail-to-tail) walls, the antiparallel coupling dominates the interaction over radial distances up to several micrometers from the centre of the domain wall., Comment: Published version, J. Phys.: Condens. Matter 19, 476204 (2007)
- Published
- 2007
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- View/download PDF
36. Nucleation of magnetisation reversal, from nanoparticles to bulk materials
- Author
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Vogel, Jan, Moritz, Jérôme, and Fruchart, Olivier
- Subjects
Condensed Matter - Other Condensed Matter - Abstract
We review models for the nucleation of magnetisation reversal, i.e. the formation of a region of reversed magnetisation in an initially magnetically saturated system. For small particles models for collective reversal, either uniform (Stoner-Wohlfarth model) or non-uniform like curling, provide good agreement between theory and experiment. For microscopic objects and thin films, we consider two models, uniform (Stoner-Wohlfarth) reversal inside a nucleation volume and a droplet model, where the free energy of an inverse bubble is calculated taking into account volume energy (Zeeman energy) and surface tension (domain wall energy). In macroscopic systems, inhomogeneities in magnetic properties cause a distribution of energy barriers for nucleation, which strongly influences effects of temperature and applied field on magnetisation reversal. For these systems, macroscopic material parameters like exchange interaction, spontaneous magnetisation and magnetic anisotropy can give an indication of the magnetic coercivity, but exact values for nucleation fields are, in general, hard to predict., Comment: 12 pages; Published in a Special Issue of the C. R. Physique devoted to nucleation. C.R. Physique 7, 977 (2006). Corrected version, as published
- Published
- 2006
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37. Influence of topography and Co domain walls on the magnetization reversal of the FeNi layer in FeNi/Al$\_2$O$\_3$/Co magnetic tunnel junctions
- Author
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Romanens, Fabien, Vogel, Jan, Kuch, Wolfgang, Fukumoto, Keiki, Camarero, Julio, Pizzini, Stefania, Bonfim, Marlio, and Petroff, Frédéric
- Subjects
Condensed Matter - Other Condensed Matter - Abstract
We have studied the magnetization reversal dynamics of FeNi/Al$\_2$O$\_3$/Co magnetic tunnel junctions deposited on step-bunched Si substrates using magneto-optical Kerr effect and time-resolved x-ray photoelectron emission microscopy combined with x-ray magnetic circular dichroism (XMCD-PEEM). Different reversal mechanisms have been found depending on the substrate miscut angle. Larger terraces (smaller miscut angles) lead to a higher nucleation density and stronger domain wall pinning. The width of domain walls with respect to the size of the terraces seems to play an important role in the reversal. We used the element selectivity of XMCD-PEEM to reveal the strong influence of the stray field of domain walls in the hard magnetic layer on the magnetic switching of the soft magnetic layer., Comment: 8 Pages, 7 Figures
- Published
- 2006
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- View/download PDF
38. Dynamics of magnetic domain wall motion after nucleation: Dependence on the wall energy
- Author
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Fukumoto, Keiki, Kuch, Wolfgang, Vogel, Jan, Romanens, Fabien, Pizzini, Stefania, Camarero, Julio, Bonfim, Marlio, and Kirschner, Jürgen
- Subjects
Condensed Matter - Other Condensed Matter - Abstract
The dynamics of magnetic domain wall motion in the FeNi layer of a FeNi/Al2O3/Co trilayer has been investigated by a combination of x-ray magnetic circular dichroism, photoelectron emission microscopy, and a stroboscopic pump-probe technique. The nucleation of domains and subsequent expansion by domain wall motion in the FeNi layer during nanosecond-long magnetic field pulses was observed in the viscous regime up to the Walker limit field. We attribute an observed delay of domain expansion to the influence of the domain wall energy that acts against the domain expansion and that plays an important role when domains are small., Comment: Accepted for publication in Physical Review Letters
- Published
- 2006
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39. Magnetic relaxation of exchange biased (Pt/Co) multilayers studied by time-resolved Kerr microscopy
- Author
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Romanens, Fabien, Pizzini, Stefania, Yokaichiya, Fabiano, Bonfim, Marlio, Pennec, Yan, Camarero, Julio, Vogel, Jan, Sort, Jordi, Garcia, Flavio, Rodmacq, Bernard, and Dieny, Bernard
- Subjects
Condensed Matter - Other Condensed Matter - Abstract
Magnetization relaxation of exchange biased (Pt/Co)5/Pt/IrMn multilayers with perpendicular anisotropy was investigated by time-resolved Kerr microscopy. Magnetization reversal occurs by nucleation and domain wall propagation for both descending and ascending applied fields, but a much larger nucleation density is observed for the descending branch, where the field is applied antiparallel to the exchange bias field direction. These results can be explained by taking into account the presence of local inhomogeneities of the exchange bias field., Comment: To appear in Physical Review B (October 2005)
- Published
- 2005
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40. Influence of domain wall interactions on nanosecond switching in magnetic tunnel junctions
- Author
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Vogel, Jan, Kuch, Wolfgang, Hertel, Riccardo, Camarero, Julio, Fukumoto, Keiki, Romanens, Fabien, Pizzini, Stefania, Bonfim, Marlio, Petroff, Frédéric, Fontaine, Alain, and Kirschner, Jürgen
- Subjects
Condensed Matter - Other Condensed Matter - Abstract
We have obtained microscopic evidence of the influence of domain wall stray fields on the nanosecond magnetization switching in magnetic trilayer systems. The nucleation barrier initiating the magnetic switching of the soft magnetic Fe20Ni80 layer in magnetic tunnel junction-like FeNi/Al2O3/Co trilayers is considerably lowered by stray fields generated by domain walls present in the hard magnetic Co layer. This internal bias field can significantly increase the local switching speed of the soft layer. The effect is visualized using nanosecond time- and layer-resolved magnetic domain imaging and confirmed by micromagnetic simulations., Comment: 5 Pages, 3 Figures. Submitted to Physical Review Letters
- Published
- 2005
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41. Magnetic relaxation measurements of exchange biased (Pt/Co) multilayers with perpendicular anisotropy
- Author
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Romanens, Fabien, Pizzini, Stefania, Sort, Jordi, Garcia, Flavio, Camarero, Julio, Yokaichiya, Fabiano, Pennec, Yan, Vogel, Jan, and Dieny, Bernard
- Subjects
Condensed Matter - Other Condensed Matter - Abstract
Magnetic relaxation measurements were carried out by magneto-optical Kerr effect on exchange biased (Pt/Co)5/Pt/FeMn multilayers with perpendicular anisotropy. In these films the coercivity and the exchange bias field vary with Pt spacer thickness, and have a maximum for 0.2 nm. Hysteresis loops do not reveal important differences between the reversal for ascending and descending fields. Relaxation measurements were fitted using Fatuzzo's model, which assumes that reversal occurs by domain nucleation and domain wall propagation. For 2 nm thick Pt spacer (no exchange bias) the reversal is dominated by domain wall propagation starting from a few nucleation centers. For 0.2 nm Pt spacer (maximum exchange bias) the reversal is strongly dominated by nucleation, and no differences between the behaviour of the ascending and descending branches can be observed. For 0.4 nm Pt spacer (weaker exchange bias) the nucleation density becomes less important, and the measurements reveal a much stronger density of nucleation centers in the descending branch., Comment: Europhysical Journal B, in print DOI: 10.1140/epjb/e2005-00053-3
- Published
- 2005
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42. Interplay between magnetic anisotropy and interlayer coupling in nanosecond magnetization reversal of spin-valve trilayers
- Author
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Vogel, Jan, Kuch, Wolfgang, Camarero, Julio, Fukumoto, Keiki, Pennec, Yan, Pizzini, Stefania, Bonfim, Marlio, Petroff, Frédéric, Fontaine, Alain, and Kirschner, Jürgen
- Subjects
Condensed Matter - Other Condensed Matter - Abstract
The influence of magnetic anisotropy on nanosecond magnetization reversal in coupled FeNi/Cu/Co trilayers was studied using a photoelectron emission microscope combined with x-ray magnetic circular dicroism. In quasi-isotropic samples the reversal of the soft FeNi layer is determined by domain wall pinning that leads to the formation of small and irregular domains. In samples with uniaxial magnetic anisotropy, the domains are larger and the influence of local interlayer coupling dominates the domain structure and the reversal of the FeNi layer.
- Published
- 2005
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43. Nanometers-thick self-organized Fe stripes: bridging the gap between surfaces and magnetic materials
- Author
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Fruchart, Olivier, Eleoui, Mustafa, Vogel, Jan, Jubert, Pierre-Olivier, Locatelli, Andrea, and Ballestrazzi, A
- Subjects
Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We have fabricated 5nm-high Fe(110) stripes by self-organized (SO) growth on a slightly vicinal R(110)/Al2O3(11-20) surface, with R=Mo, W. Remanence, coercivity and domain patterns were observed at room temperature (RT). This contrasts with conventional SO epitaxial systems, that are superparamagnetic or even non-magnetic at RT due to their flatness. Our process should help to overcome superparamagnetism without compromise on the lateral size if SO systems are ever to be used in applications.
- Published
- 2003
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44. Previously reported placebo-response-associated variants do not predict patient outcomes in inflammatory disease Phase III trial placebo arms
- Author
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Haug-Baltzell, Asher, Bhangale, Tushar R., Chang, Diana, Dressen, Amy, Yaspan, Brian L., Ortmann, Ward, Brauer, Matthew J., Hunkapiller, Julie, Reeder, Jens, Mukhyala, Kiran, Cuenco, Karen T., Tom, Jennifer A., Cowgill, Amy, Vogel, Jan, Forrest, William F., Behrens, Timothy W., Graham, Robert R., and Wuster, Arthur
- Published
- 2019
- Full Text
- View/download PDF
45. Improving Néel Domain Walls Dynamics and Skyrmion Stability Using He Ion Irradiation
- Author
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Balan, Cristina, primary, van de Jagt, Johannes W., additional, Fassatoui, Aymen, additional, Peña Garcia, Jose, additional, Jeudy, Vincent, additional, Thiaville, André, additional, Bonfim, Marlio, additional, Vogel, Jan, additional, Ranno, Laurent, additional, Ravelosona, Dafiné, additional, and Pizzini, Stefania, additional
- Published
- 2023
- Full Text
- View/download PDF
46. Cybersecurity of Hospitals: discussing the challenges and working towards mitigating the risks
- Author
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Argaw, Salem T., Troncoso-Pastoriza, Juan R., Lacey, Darren, Florin, Marie-Valentine, Calcavecchia, Franck, Anderson, Denise, Burleson, Wayne, Vogel, Jan-Michael, O’Leary, Chana, Eshaya-Chauvin, Bruce, and Flahault, Antoine
- Published
- 2020
- Full Text
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47. Enzymatic Quorum Quenching in Biofilms
- Author
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Vogel, Jan, primary and Quax, Wim J., additional
- Published
- 2019
- Full Text
- View/download PDF
48. Contributors
- Author
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Abbamondi, Gennaro Roberto, primary, Ayala-Zavala, Fernando Jesus, additional, Bellezza, Ilaria, additional, Berber, Didem, additional, Coppola, Raffaele, additional, Costantino, Valeria, additional, Cutignano, Adele, additional, d’Acierno, Antonio, additional, De Feo, Vincenzo, additional, Della Sala, Gerardo, additional, Esposito, Germana, additional, Finore, Ilaria, additional, Fratianni, Florinda, additional, Gökalsın, Barış, additional, Gomes-Cruz, Adriano, additional, Granato, Daniel, additional, Jimenez, Angel G., additional, Kambourova, Margarita, additional, Kırtel, Onur, additional, Lami, Raphaël, additional, Minelli, Alba, additional, Nazzaro, Filomena, additional, Nicolaus, Barbara, additional, Toksoy Öner, Ebru, additional, Peirce, Matthew J., additional, Poli, Annarita, additional, Quax, Wim J., additional, Sesal, Nüzhet Cenk, additional, Sperandio, Vanessa, additional, Teta, Roberta, additional, Van den Ende, Wim, additional, Versluys, Maxime, additional, and Vogel, Jan, additional
- Published
- 2019
- Full Text
- View/download PDF
49. Quorum Sensing inhibition to battle infectious diseases
- Author
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Vogel, Jan, Vogel, Jan, Vogel, Jan, and Vogel, Jan
- Abstract
Antibiotic crisis – Back to the start A famous quote of Charles Darwin reads: “It is not the strongest of the species that survives, not the most intelligent that survives. It is the one that is the most adaptable to change.” Every living creature is evolving, is adapting to changes of the environment, all the time. With the discovery of antibiotics physicians found, adapted and refined powerful compounds to efficiently kill bacteria. The overuse of antibiotics will eventually render the same useless, as we can observe already right now. Against all logic and warnings antibiotics are still being used carelessly and are expelled to the environment in large quantities. Quorum quenching (QQ) strategies with the acylase PvdQ could be an alternative or addition to conventional antibiotics. The goal of this treatment is to attenuate virulence factors and hinder the formation of biofilms. The clearance of the infection will be performed by the immune system of the host or with the help of antibacterial compounds. Applications of QQ enzymes could be the functionalization of various medical relevant surfaces to mediate anti biofilm properties. We demonstrated in this work that the QQ enzyme PvdQ has indeed the potential to be used against A. baumannii, and P. aeruginosa infections in vitro and in vivo. The potential of QQEs justifies to put more effort in research and refinement of this technique and eventually QQ treatment approaches could offer powerful tools to fight bacterial infections in the future.
- Published
- 2022
50. Control of the interaction between pinning disorder and domain walls in Pt/Co/AlOx ultrathin films by He+ ion irradiation
- Author
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Balan, Cristina, primary, van der Jagt, Johannes W., additional, Peña Garcia, Jose, additional, Vogel, Jan, additional, Ranno, Laurent, additional, Bonfim, Marlio, additional, Ravelosona, Dafiné, additional, Pizzini, Stefania, additional, and Jeudy, Vincent, additional
- Published
- 2023
- Full Text
- View/download PDF
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