Academic literature on the topic 'Skyrmion dynamics'
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Journal articles on the topic "Skyrmion dynamics"
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Yu, X. Z., D. Morikawa, K. Nakajima, et al. "Motion tracking of 80-nm-size skyrmions upon directional current injections." Science Advances 6, no. 25 (2020): eaaz9744. http://dx.doi.org/10.1126/sciadv.aaz9744.
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Nanometer-scale skyrmions are prospective candidates for information bits in low–power consumption devices owing to their topological nature and controllability with low current density. Studies on skyrmion dynamics in different classes of materials have exploited the topological Hall effect and current-driven fast motion of skyrmionic bubbles. However, the small current track motion of a single skyrmion and few-skyrmion aggregates remains elusive. Here, we report the tracking of creation and extinction and motion of 80-nm-size skyrmions upon directional one–current pulse excitations at low current density of the order of 109 A m−2 in designed devices with the notched hole. The Hall motion of a single skyrmion and the torque motions of few-skyrmion aggregates have been directly revealed. The results exemplify low–current density controls of skyrmions, which will pave the way for the application of skyrmions.
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Shimojima, Takahiro, Asuka Nakamura, Xiuzhen Yu, et al. "Nano-to-micro spatiotemporal imaging of magnetic skyrmion’s life cycle." Science Advances 7, no. 25 (2021): eabg1322. http://dx.doi.org/10.1126/sciadv.abg1322.
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Magnetic skyrmions are self-organized topological spin textures that behave like particles. Because of their fast creation and typically long lifetime, experimental verification of skyrmion’s creation/annihilation processes has been challenging. Here, we successfully track skyrmion dynamics in defect-introduced Co9Zn9Mn2 by using pump-probe Lorentz transmission electron microscope. Following the nanosecond photothermal excitation, we resolve 160-nm skyrmion’s proliferation at <1 ns, contraction at 5 ns, drift from 10 ns to 4 μs, and coalescence at ~5 μs. These motions relay the multiscale arrangement and relaxation of skyrmion clusters in a repeatable cycle of 20 kHz. Such repeatable dynamics of skyrmions, arising from the weakened but still persistent topological protection around defects, enables us to visualize the whole life of the skyrmions and demonstrates the possible high-frequency manipulations of topological charges brought by skyrmions.
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Shu, Yun, Qianrui Li, Jing Xia, et al. "Realization of the skyrmionic logic gates and diodes in the same racetrack with enhanced and modified edges." Applied Physics Letters 121, no. 4 (2022): 042402. http://dx.doi.org/10.1063/5.0097152.
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Magnetic skyrmions are topological quasiparticles with nanoscale size and high mobility, which have potential applications in information storage and spintronic devices. Here, we computationally investigate the dynamics of isolated skyrmions in a ferromagnetic racetrack, where magnetic properties of the edges are enhanced and modified, forming a channel with lower magnetic anisotropy for skyrmion motion. It is found that the rectangular notch at the edge can have a pinning effect on the skyrmion and enrich the dynamics of the skyrmion. Based on the racetrack with modified edges and the notch, we design a racetrack that realizes the skyrmionic logic AND, OR, and NOT gates as well as the diode in the same magnetic racetrack. It is found that the driving current density could be much smaller than those used in previous designs of skyrmion-based logic gates. By slightly altering the shape of the racetrack, we also design the NAND and NOR gates. Finally, we study the feasibility of our design at finite temperatures. Our results may contribute to the design of nonvolatile spintronic devices with integrated multiple functions and ultra-low energy consumption.
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Zhao, Xuebing, Chiming Jin, Chao Wang, et al. "Direct imaging of magnetic field-driven transitions of skyrmion cluster states in FeGe nanodisks." Proceedings of the National Academy of Sciences 113, no. 18 (2016): 4918–23. http://dx.doi.org/10.1073/pnas.1600197113.
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Magnetic skyrmion is a nanosized magnetic whirl with nontrivial topology, which is highly relevant for applications on future memory devices. To enable the applications, theoretical efforts have been made to understand the dynamics of individual skyrmions in magnetic nanostructures. However, directly imaging the evolution of highly geometrically confined individual skyrmions is challenging. Here, we report the magnetic field-driven dynamics of individual skyrmions in FeGe nanodisks with diameters on the order of several skyrmion sizes by using Lorentz transmission electron microscopy. In contrast to the conventional skyrmion lattice in bulk, a series of skyrmion cluster states with different geometrical configurations and the field-driven cascading phase transitions are identified at temperatures far below the magnetic transition temperature. Furthermore, a dynamics, namely the intermittent jumps between the neighboring skyrmion cluster states, is found at elevated temperatures, at which the thermal energy competes with the energy barrier between the skyrmion cluster states.
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Lin, Jia-Qiang, Ji-Pei Chen, Zhen-Yu Tan, et al. "Manipulation of Skyrmion Motion Dynamics for Logical Device Application Mediated by Inhomogeneous Magnetic Anisotropy." Nanomaterials 12, no. 2 (2022): 278. http://dx.doi.org/10.3390/nano12020278.
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Magnetic skyrmions are promising potential information carriers for future spintronic devices owing to their nanoscale size, non-volatility and high mobility. In this work, we demonstrate the controlled manipulation of skyrmion motion and its implementation in a new concept of racetrack logical device by introducing an inhomogeneous perpendicular magnetic anisotropy (PMA) via micromagnetic simulation. Here, the inhomogeneous PMA can be introduced by a capping nano-island that serves as a tunable potential barriers/well which can effectively modulate the size and shape of isolated skyrmion. Using the inhomogeneous PMA in skyrmion-based racetrack enables the manipulation of skyrmion motion behaviors, for instance, blocking, trapping or allowing passing the injected skyrmion. In addition, the skyrmion trapping operation can be further exploited in developing special designed racetrack devices with logic AND and NOT, wherein a set of logic AND operations can be realized via skyrmion–skyrmion repulsion between two skyrmions. These results indicate an effective method for tailoring the skyrmion structures and motion behaviors by using inhomogeneous PMA, which further provide a new pathway to all-electric skyrmion-based memory and logic devices.
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Bao, Bei, Mingming Yang, and Ming Yan. "Asymmetric Motion of Magnetic Skyrmions in Ferromagnetic Nanotubes Induced by a Magnetic Field." Symmetry 14, no. 6 (2022): 1195. http://dx.doi.org/10.3390/sym14061195.
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Magnetic skyrmions, featuring topological stability and low driving current density, are believed to be a promising candidate of information carriers. One of the obstacles to application is the skyrmion Hall effect, which can lead to the annihilation of moving skyrmions at the lateral boundary of thin-film tracks. In order to resolve this issue, it was recently proposed to exploit ferromagnetic nanotubes as alternative skyrmion guides. In this work, we investigate the field-effect of current-driven skyrmion motion in nanotubes using micromagnetic simulations. It is found that, in the presence of an axial field, the skyrmion motion becomes asymmetric in tubes. This is fundamentally different from the flat strip, in which a field has little influence on the skyrmion dynamics. Based on the dissipation tensor determined by the spin texture of the skyrmions, the solution of the Thiele equation is obtained, yielding a perfect match with simulations. We argue that the asymmetry of the skyrmion dynamics originates from the curvature of the nanotube.
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Coelho, Rodrigo C. V., Mykola Tasinkevych, and Margarida M. Telo da Gama. "Dynamics of flowing 2D skyrmions." Journal of Physics: Condensed Matter 34, no. 3 (2021): 034001. http://dx.doi.org/10.1088/1361-648x/ac2ca9.
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Abstract We investigate, numerically, the effects of externally imposed material flows on the structure and temporal evolution of liquid crystal (LC) skyrmions. The dynamics of a 2D system of skyrmions is modeled using the Ericksen–Leslie theory, which is based on two coupled equations, one for material flow and the other for the director field. As the time scales of the velocity and director fields differ by several orders of magnitude for realistic values of the system parameters, we have simplified the calculations by assuming that the velocity relaxes instantaneously when compared to the relaxation of the director field. Thus, we have used a finite-differences method known as artificial compressibility with adaptive time step to solve the velocity field and a fourth-order Runge-Kutta method for the director field. We characterized the skyrmion shape or configuration as a function of the time and the average velocity of the flow field. We found that for velocities above a certain threshold, the skyrmions stretch in the direction perpendicular to the flow, by contrast to the regime of weak flows where the skyrmions stretch along the streamlines of the flow field. These two regimes are separated by an abrupt (first-order) dynamical transition, which is robust with respect to e.g., the LC elastic anisotropy. Additionally, we have found how the presence of a second skyrmion affects the evolution of the shape of the skyrmions, by comparing the evolution of pairs of skyrmions to the evolution of a single-skyrmion.
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Coelho, Rodrigo C. V., Mykola Tasinkevych, and Margarida M. Telo da Gama. "Dynamics of flowing 2D skyrmions." Journal of Physics: Condensed Matter 34, no. 3 (2021): 034001. http://dx.doi.org/10.1088/1361-648x/ac2ca9.
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Abstract We investigate, numerically, the effects of externally imposed material flows on the structure and temporal evolution of liquid crystal (LC) skyrmions. The dynamics of a 2D system of skyrmions is modeled using the Ericksen–Leslie theory, which is based on two coupled equations, one for material flow and the other for the director field. As the time scales of the velocity and director fields differ by several orders of magnitude for realistic values of the system parameters, we have simplified the calculations by assuming that the velocity relaxes instantaneously when compared to the relaxation of the director field. Thus, we have used a finite-differences method known as artificial compressibility with adaptive time step to solve the velocity field and a fourth-order Runge-Kutta method for the director field. We characterized the skyrmion shape or configuration as a function of the time and the average velocity of the flow field. We found that for velocities above a certain threshold, the skyrmions stretch in the direction perpendicular to the flow, by contrast to the regime of weak flows where the skyrmions stretch along the streamlines of the flow field. These two regimes are separated by an abrupt (first-order) dynamical transition, which is robust with respect to e.g., the LC elastic anisotropy. Additionally, we have found how the presence of a second skyrmion affects the evolution of the shape of the skyrmions, by comparing the evolution of pairs of skyrmions to the evolution of a single-skyrmion.
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Brearton, Richard, Maciej W. Olszewski, Shilei Zhang, et al. "Skyrmions in anisotropic magnetic fields: strain and defect driven dynamics." MRS Advances 4, no. 11-12 (2019): 643–50. http://dx.doi.org/10.1557/adv.2019.43.
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ABSTRACTMagnetic skyrmions are particle-like, topologically protected magnetization entities that are promising candidates for information carriers in racetrack-memory schemes. The transport of skyrmions in a shift-register-like fashion is crucial for their embodiment in practical devices. Recently, we demonstrated experimentally that chiral skyrmions in Cu2OSeO3 can be effectively manipulated by a magnetic field gradient, leading to a collective rotation of the skyrmion lattice with well-defined dynamics in a radial field gradient. Here, we employ a skyrmion particle model to numerically study the effects of resultant shear forces on the structure of the skyrmion lattice. We demonstrate that anisotropic peak broadening in experimentally observed diffraction patterns can be attributed to extended linear regions in the magnetic field profile. We show that topological (5-7) defects emerge to protect the six-fold symmetry of the lattice under the application of local shear forces, further enhancing the stability of proposed magnetic field driven devices.
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Li, Yang, and Hua Pang. "The skyrmion annihilations induced by local reversal of background field in a skyrmion lattice." Journal of Physics D: Applied Physics 55, no. 20 (2022): 205303. http://dx.doi.org/10.1088/1361-6463/ac4a39.
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Abstract The understanding of the creation and annihilation dynamics of a magnetic skyrmion is significant due to its potential applications in information storage and spintronics. Although there have been extensive investigations on the annihilation of isolated skyrmions, topological annihilation in a periodic skyrmion lattice is a more complex process. We report a micromagnetic simulation study about the annihilation process of a two-dimensional (2D) skyrmion triangular lattice triggered by a uniform field H REV of comparable size to the skyrmion, which is opposite to the direction of the background field, revealing two annihilation modes. When the H REV center is within the range of a skyrmion, the neighboring skyrmions annihilate in-situ, while the center is between adjacent skyrmions, an anti-skyrmion is induced in the interstitial region. Both mechanisms tend to experience the intermediate topological vortex or antivortex structure, and the spin system undergoes a long period of relaxation to reach a stable state after the topological charge is stabilized. Our results present a local annihilation scheme that is easy to achieve in a 2D skyrmion lattice and highlight the role of interaction between skyrmions in the transformation between different kinds of topological defects.
Dissertations / Theses on the topic "Skyrmion dynamics"
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Velkov, Hristo [Verfasser]. "Skyrmion dynamics in antiferromagnets / Hristo Velkov." Mainz : Universitätsbibliothek Mainz, 2018. http://d-nb.info/1160488932/34.
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Bamler, Robert Verfasser], Achim [Gutachter] Rosch, and Alexander [Gutachter] [Altland. "Phase-Space Berry Phases in Chiral Magnets: Skyrmion Charge, Hall Effect, and Dynamics of Magnetic Skyrmions / Robert Bamler. Gutachter: Achim Rosch ; Alexander Altland." Köln : Universitäts- und Stadtbibliothek Köln, 2016. http://d-nb.info/1113178728/34.
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Legrand, William. "Crafting magnetic skyrmions at room temperature : size, stability and dynamics in multilayers." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS066/document.
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Les skyrmions magnétiques sont des enroulements bidimensionnels et nanométriques de la configuration de spin, pouvant être stabilisés dans certains matériaux magnétiques soumis à l’interaction d’échange antisymétrique Dzyaloshinskii-Moriya. Ils présentent une topologie non-triviale et s’annoncent peut-être comme étant les plus petites configurations magnétiques pouvant être réalisées. Très récemment, des skyrmions magnétiques ont pu être stabilisés à température ambiante grâce à la conception de multicouches magnétiques brisant la symétrie d’inversion selon la direction verticale. Suite à cette avancée, l’objectif central de cette thèse est la compréhension et la maîtrise des multiples propriétés physiques des skyrmions hébergés dans ces systèmes multicouches. Pour aborder cet objectif, un modèle original est décrit puis employé, permettant la prédiction des profils adoptés par les skyrmions multicouches. Ce modèle numérique est très générique, n’utilisant que la symétrie cylindrique des skyrmions afin de simplifier la détermination des interactions magnétostatiques. Ce modèle est ensuite étendu afin de pouvoir approximer la stabilité thermique des skyrmions, ce qui constitue un élément clé dans leur obtention expérimentale. Une seconde dimension de ce travail consiste en l’étude expérimentale de la manipulation électrique des skyrmions multicouches, démontrant la possibilité de trois fonctionnalités centrales que sont leur nucléation par courants locaux, leur déplacement sous courant de spin et leur détection électrique individuelle par tension transverse. Le troisième aspect de ma thèse est l’étude des propriétés physiques influençant le déplacement des skyrmions dans les multicouches magnétiques. Un comportement d’ancrage sur des défauts est mis en évidence expérimentalement et est analysé à l’aide d’une modélisation micromagnétique. Un des résultats importants de ce travail est aussi la prédiction d’une chiralité hybride dans les configurations magnétiques de certaines multicouches, qui est ensuite démontrée expérimentalement par des mesures au synchrotron. Les conséquences attendues de cette chiralité hybride sur le déplacement des skyrmions sont étudiées pour permettre l’optimisation des multicouches, aboutissant à l’observation expérimentale de la propagation de skyrmions de 50 nm de rayon à des vitesses atteignant environ 40 m/s. La dernière partie de cette thèse vise à mettre à profit ces avancées théoriques et expérimentales afin de parvenir à réduire la taille des skyrmions à température ambiante. Après avoir analysé l’impact des interactions dipolaires sur la stabilité des skyrmions, il est entrepris d’optimiser les matériaux et la périodicité des couches. Je m’intéresse aussi à la conception expérimentale de textures magnétiques dont l’aimantation est compensée au sein de structures multicouches appelées antiferromagnétiques synthétiques, dont je montre qu’elles peuvent héberger des skyrmions antiferromagnétiques à température ambiante. Ce résultat final ouvre de nouvelles perspectives vers l’obtention de skyrmions à la fois mesurant moins de 10 nm et très mobiles, qui pourraient être utilisés dans la conception de composants de calcul et de stockage d’information plus compacts et plus efficaces<br>Magnetic skyrmions are nanoscale two-dimensional windings in the spin configuration of some magnetic materials subject to the Dzyaloshinskii-Moriya antisymmetric exchange interaction. They feature a non-trivial topology and show promise to be the smallest achievable magnetic textures. Very recently, magnetic skyrmions have been successfully stabilised up to room temperature by leveraging on the design of magnetic multilayer systems breaking the vertical inversion symmetry. Following up on this achievement, the main objective of this thesis is the understanding and the control of the various physical properties of skyrmions hosted by such multilayer systems. As a first approach to this objective, an original model allowing to predict the profiles adopted by multilayer skyrmions is described and then employed. This numerical model is very generic, as it exploits only the cylindrical symmetry of multilayer skyrmions, in order to determine the magnetostatic interactions with less effort. This model is further extended in order to approximate the thermal stability of multilayer skyrmions, which is key to their experimental realisation. The next aspect of this thesis consists in the experimental study of the electrical manipulation of multilayer skyrmions, demonstrating three main functionalities that are nucleation by local currents, displacement under spin currents and individual detection by transverse voltage. The third aspect of my thesis is the study of the physical properties influencing the current-induced motion of skyrmions in magnetic multilayers. A pinning behaviour is evidenced experimentally and analysed relying on micromagnetic modelling. One of the important results of this work is also the prediction of hybrid chirality for some multilayer magnetic configurations, which is then demonstrated experimentally using a synchrotron technique. The impact of hybrid chirality on current-induced skyrmion motion is discussed and leads to the optimisation of the multilayer design, resulting in the experimental observation of motion for skyrmions below 50 nm in radius at velocities reaching around 40 m/s. The last part of this thesis aims at leveraging on these theoretical and experimental advances in order to reduce the size of skyrmions at room temperature. After the analysis of the impact of dipolar interactions on skyrmion stability, the engineering of the materials and of the layers periodicity is attempted. I also investigate experimentally the conception of magnetic textures with compensated magnetization in multilayer structures known as synthetic antiferromagnets, and show that they can host antiferromagnetic skyrmions at room temperature. This last result opens up new prospects for achieving room-temperature skyrmions combining size in the single-digit nm range and high mobility, potentially allowing applications towards energy-efficient computation and storage devices with a very dense integration
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Chen, Xing. "Modeling and simulations of skyrmionic neuromorphic applications." Thesis, université Paris-Saclay, 2022. http://www.theses.fr/2022UPAST083.
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Les nanodispositifs spintroniques, qui exploitent à la fois les propriétés magnétiques et électriques des électrons, apportent diverses caractéristiques intéressantes et prometteuses pour le calcul neuromorphique. Les textures magnétiques, telles que les parois de domaine et les skyrmions, sont particulièrement intrigantes en tant que composants neuromorphiques, car elles peuvent prendre en charge différentes fonctionnalités grâce à la richesse de leurs mécanismes physiques. La façon dont la dynamique des skyrmions peut être utilisée pour construire du matériel neuromorphique économe en énergie, et comment l'apprentissage profond peut aider à réaliser des tests et des validations rapides et précis des propositions constituent les sujets centraux de cette thèse. Les principales contributions et innovations de cette thèse peuvent être résumées comme suit : 1. Études numériques et théoriques sur la dynamique des skyrmions dans les nanostructures confinées. Nous explorons la dynamique des skyrmions en termes de taille, de vitesse, d'énergie et de stabilité dans une nanopiste dont la largeur varie. Nous avons constaté que des skyrmions de petite taille pouvaient être obtenus en utilisant cette structure asymétrique. Nous obtenons également un compromis entre la largeur de la nanopiste (densité de stockage) et la vitesse de mouvement du skyrmion (vitesse d'accès aux données). Nous étudions la dynamique du skyrmion sous excitation de tension par l'effet d'anisotropie magnétique contrôlé par la tension dans un film mince circulaire. Nous constatons que le skyrmion respirant peut être analogisé comme un modulateur. Ces résultats pourraient nous aider à concevoir des dispositifs neuromorphiques efficaces. 2. Applications des dispositifs basés sur le skyrmion pour l'informatique neuromorphique. Nous présentons un dispositif compact de neurones de dopage Leaky-Integrate-Fire en exploitant la dynamique du skyrmion entraînée par le courant dans un nanotrack cunéiforme. Nous proposons un générateur de nombres aléatoires véritables basé sur le mouvement brownien thermique continu du skyrmion dans une géométrie confinée à température ambiante. Notre conception est prometteuse pour les systèmes de calcul neuromorphique émergents à faible puissance, tels que les réseaux neuronaux à impulsions et les réseaux neuronaux de calcul stochastique/probabiliste.3. Une approche axée sur les données pour la modélisation des systèmes physiques dynamiques basée sur les équations différentielles ordinaires (ODE) neuronales. Nous montrons que les formalismes adaptés des ODEs neurales, conçus pour la spintronique, peuvent prédire avec précision le comportement d'un nanodispositif non idéal, y compris le bruit, après entraînement sur un ensemble minimal de simulations micromagnétiques ou de données expérimentales, avec de nouvelles entrées et de nouveaux paramètres matériels n'appartenant pas aux données d'entraînement. Grâce à cette stratégie de modélisation, nous pouvons effectuer des tâches de calcul plus complexes, telles que les prédictions de séries temporelles Mackey-Glass et la reconnaissance de chiffres parlés, en utilisant les modèles entraînés de systèmes spintroniques, avec une précision élevée et une vitesse rapide par rapport aux simulations micromagnétiques conventionnelles<br>Spintronics nanodevices, which exploit both the magnetic and electrical properties of electrons, have emerged to bring various exciting characteristics promising for neuromorphic computing. Magnetic textures, such as domain walls and skyrmions, are particularly intriguing as neuromorphic components because they can support different functionalities due to their rich physical mechanisms. How the skyrmion dynamics can be utilized to build energy efficient neuromorphic hardware, and how deep learning can help achieve fast and accurate tests and validations of the proposals form the central topics of this thesis. The major contributions and innovations of this thesis can be summarized as follows: 1. Numerical and theoretical studies on skyrmion dynamics in confined nanostructures. We explore the skyrmion dynamics in terms of size, velocity, energy, and stability in a width-varying nanotrack. We found nanoscale skyrmion with small sizes could be obtained by employing this asymmetric structure. We also obtain a tradeoff between the nanotrack width (storage density) and the skyrmion motion velocity (data access speed). We study the skyrmion dynamics under voltage excitation through the voltage-controlled magnetic anisotropy effect in a circular thin film. We find that the breathing skyrmion can be analogized as a modulator. These findings could help us design efficient neuromorphic devices. 2. Skyrmion based device applications for neuromorphic computing. We present a compact Leaky-Integrate-Fire spiking neuron device by exploiting the current-driven skyrmion dynamics in a wedge-shaped nanotrack. We propose a True random number generators based on continuous skyrmion thermal Brownian motion in a confined geometry at room temperature. Our design are promising in emerging low power neuromorphic computing system, such as spiking neural network and stochastic/ probabilistic computing neuron network.3. A data-driven approach for modeling dynamical physical systems based on the Neural Ordinary Differential Equations (ODEs). We show that the adapted formalisms of Neural ODEs, designed for spintronics, can accurately predict the behavior of a non-ideal nanodevice, including noise, after training on a minimal set of micromagnetic simulations or experimental data, with new inputs and material parameters not belonging to the training data. With this modeling strategy, we can perform more complicated computational tasks, such as Mackey-Glass time-series predictions and spoken digit recognition, using the trained models of spintronic systems, with high accuracy and fast speed compared to conventional micromagnetic simulations
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Juge, Roméo. "Nucléation et dynamique de skyrmions magnétiques dans des films ultra-minces." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALY005.
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Les skyrmions magnétiques sont des enroulements chiraux de l'aimantation que l'on peut visualiser comme de minuscules domaines magnétiques circulaires délimités par des parois de domaine chirales. En raison de leur taille potentiellement nanométrique et car on leur prédit un déplacement efficace sous courant, les skyrmions magnétiques sont devenus des candidats prometteurs pour transporter l'information dans des mémoires et des dispositifs logiques non-volatiles et à forte densité de stockage. Ils ont récemment été observés à température ambiante dans des empilements du type métal lourd/ferromagnétique/non-magnétique, franchissant une étape importante en vue de développer des dispositifs utilisant des skyrmions. Suivant ces premières observations, l'objectif de cette thèse est d'étudier certaines propriétés clés des skyrmions que sont leur nucléation, leur stabilité ainsi que leur déplacement sous courant, toutes à température ambiante. Les premiers résultats présentés portent sur la nucléation de skyrmions dans des films ultra-minces (pour une épaisseur de ferromagnétique de l'ordre de 1 nm) réalisée par ingénierie des propriétés magnétiques aux interfaces ainsi que de la géométrie des échantillons. La nucléation de skyrmions dans des films ultra-minces étendus, en géométrie confinée, dans des films polarisés par échange inter-couche puis dans des motifs définis par irradiation d'ions est présentée. La deuxième partie de ce travail concerne l'étude de la dynamique des skyrmions magnétiques sous courant. Dans un film ultra-mince de composition Pt/Co/MgO, on mesure des vitesses atteignant 100 m/s pour des tailles de skyrmions de l'ordre de 100 nm. Cette étude met également en lumière l'effet Hall de skyrmion, effet signature de leur topologie décrivant la déviation de la trajectoire d'un skyrmion par rapport à celle dictée par le courant. Nous trouvons que cette déviation dépend nettement de la vitesse des skyrmions, contrairement à ce que prédisent les modèles existants. En combinant modèle analytique et simulations micromagnétiques et en s'appuyant sur une caractérisation poussée des propriétés du film, nous trouvons que cette dépendance avec la vitesse peut être entièrement attribuée à des effets de piégeage qui entravent le déplacement des skyrmions. Enfin, la dernière partie de ce travail porte sur l'étude expérimentale de multi-couches antiferromagnétiques synthétiques, caractérisées par un moment magnétique net nul. Dans ces systèmes, on s'attend à ce que le déplacement des skyrmions s'effectue dans la direction du courant, c'est-à-dire sans effet Hall de skyrmion, une condition requise pour les applications. L'optimisation de multi-couches spécifiques permet l'observation en microscopie à rayons X de skyrmions antiferromagnétiques synthétiques de l'ordre de 100 nm. Puisque leur nucléation est délicate, un dispositif est par la suite conçu pour injecter localement du courant électrique à travers des pointes. Ce dispositif permet de créer et de supprimer des skyrmions de manière contrôlée en utilisant uniquement du courant, rapprochant ces skyrmions un peu plus des applications<br>Magnetic skyrmions are chiral magnetisation windings that can be pictured as minuscule circular magnetic domains bounded by chiral domain walls. Owing to their potential nanometre size and predicted efficient current-driven motion, magnetic skyrmions hold great promise as future information carriers in high-density non-volatile memory and logic applications. Their recent observation at room temperature in material stacks consisting of heavy metal/ferromagnet/non-magnet has lifted an important bottleneck towards the practical realisation of skyrmion-based devices. Following these early observations, the objective of this work is to tackle certain key attributes of magnetic skyrmions that are their nucleation, stability and current-driven motion, all at room temperature. The first results presented in this thesis deal with the stabilisation and nucleation of skyrmions in ultra-thin films (for a ferromagnetic thickness around 1 nm) by engineering of the interfacial magnetic properties and geometries. The nucleation of skyrmions in extended films, confined geometries, exchange-biased films and ion-irradiated films are presented. The second part of this work concerns the current-driven dynamics of magnetic skyrmions. In an ultra-thin Pt/Co/MgO film, we measure velocities up to 100 m/s for skyrmion sizes in the range of 100 nm. This study further highlights the skyrmion Hall effect, a hallmark of the skyrmion topology, which describes the deflection of a skyrmion trajectory from that imposed by the current. The angle of deflection is found to be dependent on the skyrmion velocity, in contrast with existing models. Combining analytical modelling and micromagnetic simulations, based on a thorough characterisation of the film properties, we find that this dependence on the velocity can be entirely attributed to pinning effects hindering the skyrmion motion. Finally, in the last part of this work, we investigate experimentally synthetic antiferromagnetic multi-layers with vanishing magnetic moment. In such systems, magnetic skyrmions are expected to be driven along the current direction without skyrmion Hall effect, a prerequisite for applications. By optimising specific multilayers and using X-ray microscopy, we observe synthetic antiferromagnetic skyrmions at room temperature with sizes in the range of 100 nm. As their nucleation is somewhat challenging, a device is then designed to locally inject current through patterned tips. This allows to create and delete skyrmions in a controlled fashion using solely current, bringing them one step closer to applications
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Lemesh, Ivan. "Static and dynamic properties of magnetic Skyrmions in engineered multilayer films." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122179.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2019<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 205-219).<br>Magnetic textures known as skyrmions promise new breakthroughs in memory, logic, and neuromorphic applications. Skyrmions have been found in a variety of material systems, yet there existed no experimental evidence of a material that could simultaneously host them at room temperature and also allow for their reproducible current-induced nucleation and motion. One main goal of this thesis is to fill this gap and demonstrate all the aforementioned properties in the introduced here [Pt/CoFeB/MgO]₁₅ thin film heterostructures, consisting of a perpendicularly magnetized ferromagnetic layer (M), a heavy metal (H), and a symmetry-breaking spacer layer (S). Here, I developed, fabricated, and characterized the [Pt/CoFeB/MgO]₁₅ multilayers with an extremely low density of pinning centers, which enable not only a fully reproducible skyrmion motion but also a clean study of the skyrmion nucleation process. By using X-ray microscopy, I performed the imaging of various magnetic textures in these multilayers and studied their current-induced generation and motion as a function of applied field and temperature. Finally, another goal of this work is to establish a direct link between the properties of these [H/M/S][subscript N]-type materials and the structure of magnetic textures that they can host. The energetics of such systems is understood very poorly due to the very complex multilayer stray fields and up until now, most of their analysis involved the exclusive use of micromagnetic simulations. Here, I develop an alternative theoretical approach by calculating all the stray field interactions analytically, which enables the prediction of the exact structure and dynamics of magnetic domain walls, domains, and skyrmions. Thesis<br>"Support of the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under Award No. DE-SC0012371, and of the DARPA TEE program"--page 7.<br>by Ivan Lemesh.<br>Ph. D.<br>Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering
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Brown, Bart Lee II. "Pattern formations and relaxation dynamics in non-equilibrium systems." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/89346.
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We present an investigation of two non-equilibrium systems: spatial many-species predator-prey games and systems of interacting magnetic skyrmions.
We numerically study two predator-prey systems characterized by nested pattern formations. We first consider a six species game in which spiral patterns spontaneously form within coarsening domains. Through a systematic investigation of relevant correlation functions, the interface width, and other quantities, we show that the non-trivial in-domain dynamics affect the coarsening process and the interfacial properties. The exponents which govern domain growth, aging, and interface fluctuations differ from those expected from curvature driven coarsening. The response to perturbations of the reaction rates is also studied. Furthermore, we introduce a nine species model characterized by nested spiral pattern formations. Quantitative evidence of the existence of two length and time scales associated to the spiral levels is presented in the form of correlation lengths and a temporal Fourier analysis of the species densities. A generalized interaction scheme is proposed for dynamically generated hierarchies.
Magnetic skyrmions are particle-like spin configurations found in certain chiral magnets. We study the effect of the Magnus force on the relaxation dynamics through Langevin molecular dynamics simulations. The Magnus force enhances the disorder of the system at high noise strengths while we observe a dynamic regime with slow decaying correlations at low noise strengths. The different regimes are characterized by changes in the aging exponent. In general, the Magnus force accelerates the approach to the steady state. In the presence of quenched disorder, we find that the relaxation dynamics are more robust in systems with a strong Magnus force. We also examine periodically driven skyrmion systems and show that a transition from reversible to irreversible flow exists in the presence of attractive defects. The Magnus force enhances the irreversible regime in this case.
The work on predator-prey systems was supported by the U.S. National Science Foundation through Grant No. DMR-1606814 whereas the work on skyrmions was supported by the US Department of Energy, Office of Basic Energy Sciences (DOE-BES), under Grant No. DE-FG02-09ER46613.<br>Doctor of Philosophy<br>We present an investigation of two non-equilibrium systems: spatial many-species predator- prey games and systems of interacting magnetic skyrmions. We numerically study two predator-prey systems characterized by nested pattern formations. We first consider a six species game in which spiral patterns spontaneously form within coarsening domains. Through a systematic investigation of relevant correlation functions, the interface width, and other quantities, we show that the non-trivial in-domain dynamics affect the coarsening process and, to a greater extent, properties at the interface between competing groups of species. The exponents which govern domain growth, aging, and interface fluctuations are shown to differ from those expected in typical games of competition. We also study the change of the system due to a perturbation of the reaction rates, which could represent an abrupt change in the environment. Furthermore, we introduce a nine species model characterized by the emergence of nested spiral pattern formations. Quantitative evidence of the existence of two distinct spiral levels is presented. We also propose a generalized interaction scheme for dynamically generated spiral hierarchies. Magnetic skyrmions are particle-like spin configurations found in certain chiral magnets. We study the effect of the Magnus force on the dynamic properties of skyrmion systems through particle-based simulations. The Magnus force enhances the disorder of the system at high noise strengths while accelerating the formation of the triangular lattice at low noise strengths. We find that, in general, the Magnus force accelerates the approach to the steady state. In the presence of randomly placed attractive pinning sites, we find that a strong Magnus force can prevent caging effects and allow skyrmions to more easily move around pinning sites. We also examine periodically driven skyrmion systems and show that a transition from reversible to irreversible flow exists in the presence of attractive defects. The Magnus force is shown to enhance the irreversible regime in this case. The work on predator-prey systems was supported by the U.S. National Science Foundation through Grant No. DMR-1606814 whereas the work on skyrmions was supported by the US Department of Energy, Office of Basic Energy Sciences (DOE-BES), under Grant No. DE-FG02-09ER46613.
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Büttner, Felix [Verfasser]. "Topological mass of magnetic Skyrmions probed by ultrafast dynamic imaging / Felix Büttner." Mainz : Universitätsbibliothek Mainz, 2013. http://d-nb.info/1046249096/34.
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Everschor, Karin [Verfasser], Achim [Akademischer Betreuer] Rosch, Matthias [Akademischer Betreuer] Vojta, and Stefan [Akademischer Betreuer] Blügel. "Current-Induced Dynamics of Chiral Magnetic Structures: Skyrmions, Emergent Electrodynamics and Spin-Transfer Torques / Karin Everschor. Gutachter: Achim Rosch ; Matthias Vojta ; Stefan Blügel." Köln : Universitäts- und Stadtbibliothek Köln, 2012. http://d-nb.info/103826605X/34.
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Stasinopoulos, Ioannis [Verfasser], Dirk [Akademischer Betreuer] [Gutachter] Grundler, and Christian [Gutachter] Pfleiderer. "Low damping and linearly polarized GHz magnetization dynamics in the chiral magnet Cu2OSeO3 hosting spin helices and skyrmions / Ioannis Stasinopoulos ; Gutachter: Dirk Grundler, Christian Pfleiderer ; Betreuer: Dirk Grundler." München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1131253833/34.
Full textBooks on the topic "Skyrmion dynamics"
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Eriksson, Olle, Anders Bergman, Lars Bergqvist, and Johan Hellsvik. Skyrmions. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198788669.003.0010.
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An important application of spin dynamics is the response of a magnetic material subjected to an external stimuli. In the previous chapter we discussed the response of primarily ferromagnets to temperature fluctuations that manifest itself to spin excitations and magnons. In this chapter, we are concerned about magnetic materials with more complicated magnetic texture, such as spin spirals and topological magnetic structures, in particular magnetic skyrmions. Magnetic skyrmions has many appealing and intriguing features that make them interesting both for possible applications but also from a pure theoretical point of view.
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Antos, R., and Y. Otani. The dynamics of magnetic vortices and skyrmions. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198787075.003.0022.
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This chapter argues that control of magnetic domains and domain wall structures is one of the most important issues from the viewpoint of both applied and basic research in magnetism. Its discussion is however limited to static and dynamic properties of magnetic vortex structures. It has been revealed both theoretically and experimentally that for particular ranges of dimensions of cylindrical and other magnetic elements, a curling in-plane spin configuration is energetically favored, with a small region of the out-of-plane magnetization appearing at the core of the vortex. Such a system, which is sometimes referred to as a magnetic soliton, is characterized by two binary properties: A chirality and a polarity, each of which suggests an independent bit of information in future high-density nonvolatile recording media.
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Eriksson, Olle, Anders Bergman, Lars Bergqvist, and Johan Hellsvik. Atomistic Spin Dynamics. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198788669.001.0001.
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The purpose of this book is to provide a theoretical foundation and an understanding of atomistic spin-dynamics, and to give examples of where the atomistic Landau-Lifshitz-Gilbert equation can and should be used. The contents involve a description of density functional theory both from a fundamental viewpoint as well as a practical one, with several examples of how this theory can be used for the evaluation of ground state properties like spin and orbital moments, magnetic form-factors, magnetic anisotropy, Heisenberg exchange parameters, and the Gilbert damping parameter. This book also outlines how interatomic exchange interactions are relevant for the effective field used in the temporal evolution of atomistic spins. The equation of motion for atomistic spin-dynamics is derived starting from the quantum mechanical equation of motion of the spin-operator. It is shown that this lead to the atomistic Landau-Lifshitz-Gilbert equation, provided a Born-Oppenheimer-like approximation is made, where the motion of atomic spins is considered slower than that of the electrons. It is also described how finite temperature effects may enter the theory of atomistic spin-dynamics, via Langevin dynamics. Details of the practical implementation of the resulting stochastic differential equation are provided, and several examples illustrating the accuracy and importance of this method are given. Examples are given of how atomistic spin-dynamics reproduce experimental data of magnon dispersion of bulk and thin-film systems, the damping parameter, the formation of skyrmionic states, all-thermal switching motion, and ultrafast magnetization measurements.
Book chapters on the topic "Skyrmion dynamics"
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Büttner, Felix, and Mathias Kläui. "Chapter 8 Magnetic Skyrmion Dynamics." In Skyrmions. CRC Press, 2016. http://dx.doi.org/10.1201/9781315284170-9.
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Garst, Markus. "Topological Skyrmion Dynamics in Chiral Magnets." In Topological Structures in Ferroic Materials. Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-25301-5_2.
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Yokouchi, Tomoyuki. "Current-Induced Dynamics of Skyrmion Strings Investigated by Nonreciprocal Hall Effect." In Springer Theses. Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-32-9385-4_5.
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Mochizuki, Masahito. "Current-Driven Dynamics of Skyrmions." In Topological Structures in Ferroic Materials. Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-25301-5_3.
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Stier, Martin, and Michael Thorwart. "Nonequilibrium Quantum Dynamics of Current-Driven Magnetic Domain Walls and Skyrmions." In Atomic- and Nanoscale Magnetism. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-99558-8_16.
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Jena, Jagannath. "Stability, Collapse Dynamics and Fractional Form of Antiskyrmions and Elliptical Bloch Skyrmions." In Discovery of Co-existing Non-collinear Spin Textures in D2d Heusler Compounds. Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-03910-2_6.
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Mochizuki, Masahito. "Microwave-Driven Dynamics of Magnetic Skyrmions Under a Tilted Magnetic Field: Magnetic Resonances, Translational Motions, and Spin-Motive Forces." In Topics in Applied Physics. Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-62844-4_8.
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"Magnetic Skyrmion Dynamics." In Skyrmions. CRC Press, 2016. http://dx.doi.org/10.1201/9781315284170-17.
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"Skyrmion Dynamics in Chiral Magnets." In Skyrmions. CRC Press, 2016. http://dx.doi.org/10.1201/9781315284170-18.
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Kumar Rajagopal, Rajesh. "Skyrmions in Thin Films, Interfaces and Antiferromagnetism." In Magnetic Skyrmions. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97636.
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Magnetic skyrmions are small whirling topological defects in a texture magnetization state. Their stabilization and dynamics depend strongly on their topological properties. Skyrmions are induced by non-centrosymmetric crystal structure of magnetic compounds and thin films. Skyrmions are extremely small, with diameters in the nanometer range, and behave as particles that can be created, moved and annihilated. This makes them suitable for information storage and logic technologies. Skyrmions had been observed only at low temperature, and mostly under large applied magnetic fields. An intense research in this field has led to the identification of skyrmions in thin-film and multilayer structures in these heterostrutres skyrmions are able to survive at room temperature and can be manipulated by electrical currents. Utilizing interlayer magnetic exchange bias with synthetic antiferromagnet with can be used to isolated antiferromagnetic skyrmions at room temperature. The development of skyrmion-based topological spintronics holds promise for applications in the writing, processing and reading functionalities at room temperature and can be extended further to all-electrical manipulation spintronics.
Conference papers on the topic "Skyrmion dynamics"
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Abbout, Adel, Joseph Weston, Xavier Waintal, and Aurelien Manchon. "Skyrmion dynamics and electron pumping (Conference Presentation)." In Spintronics XII, edited by Henri-Jean M. Drouhin, Jean-Eric Wegrowe, and Manijeh Razeghi. SPIE, 2019. http://dx.doi.org/10.1117/12.2525597.
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Martinez, J. C. "Current-induced dynamics in a skyrmion lattice." In 2015 IEEE International Magnetics Conference (INTERMAG). IEEE, 2015. http://dx.doi.org/10.1109/intmag.2015.7157368.
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Frank, Bettina, Timothy J. Davis, David Janoschka, Pascal Dreher, Frank J. Meyer zu Heringdorf, and Harald Giessen. "Ultrafast vector imaging of plasmonic skyrmion dynamics." In Ultrafast Phenomena and Nanophotonics XXV, edited by Markus Betz and Abdulhakem Y. Elezzabi. SPIE, 2021. http://dx.doi.org/10.1117/12.2576417.
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Pumama, I., G. W. Shiguang, W. L. Gan, and W. S. Lew. "Shape-Dependent Skyrmion Dynamics Under Spin-Orbit Torque." In 2016 International Conference of Asian Union of Magnetics Societies (ICAUMS). IEEE, 2016. http://dx.doi.org/10.1109/icaums.2016.8479891.
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Carpentieri, M., R. Tomasello, G. Finocchio, and R. Zivieri. "Topological skyrmion dynamics driven by spin-transfer torque." In 2015 IEEE International Magnetics Conference (INTERMAG). IEEE, 2015. http://dx.doi.org/10.1109/intmag.2015.7156848.
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Lee, Seung-Jae, and Kyung-Jin Lee. "Current Induced Skyrmion Dynamics via Spin Orbit Coupling Types." In 2016 International Conference of Asian Union of Magnetics Societies (ICAUMS). IEEE, 2016. http://dx.doi.org/10.1109/icaums.2016.8479696.
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Zhang, X., J. Xia, Y. Zhou, X. Liu, H. Zhang, and M. Ezawa. "Current-induced skyrmion dynamics in a frustrated magnetic film." In 2018 IEEE International Magnetic Conference (INTERMAG). IEEE, 2018. http://dx.doi.org/10.1109/intmag.2018.8508053.
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Klaui, M. "Skyrmion Dynamics – from thermal diffusion to ultra-fast motion." In 2018 IEEE International Magnetic Conference (INTERMAG). IEEE, 2018. http://dx.doi.org/10.1109/intmag.2018.8508806.
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Fook, H., C. Ang Ching Ian, W. Gan, I. Purnama, and W. Lew. "Mitigation of magnus force in current-induced skyrmion dynamics." In 2015 IEEE International Magnetics Conference (INTERMAG). IEEE, 2015. http://dx.doi.org/10.1109/intmag.2015.7157020.
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Langner, Matt, Sujoy Roy, S. Mishra, et al. "Ultrafast Dynamics of the Skyrmion and Conical Phases in Cu2OSeO3." In CLEO: QELS_Fundamental Science. OSA, 2015. http://dx.doi.org/10.1364/cleo_qels.2015.fw3b.5.
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