scholarly journals Quantitative behavior study of velocity, radius and topological charge on skyrmion/edge interaction dynamics on Co/Pt nanotrack

2020 ◽  
Vol 3 (1) ◽  
pp. 50-65
Author(s):  
Isaac Andrade Santece ◽  
Josiel Carlos Souza Gomes ◽  
Danilo Toscano ◽  
Maxwel Gama Monteiro Jr. ◽  
João Paulo Almeida de Mendonça ◽  
...  
Keyword(s):  
Electric Current ◽  
Data Storage ◽  
Topological Charge ◽  
Perpendicular Magnetic Anisotropy ◽  
Point Of View ◽  
Critical Position ◽  
Micromagnetic Simulations ◽  
Spintronic Devices ◽  
Limit Value ◽  
Magnus Effect

Skyrmions are considered promising candidates to be the information carriers in the next generation of data storage and logic devices, due to its stability and easy control under the application of an electric current. For future technological applications in spintronic devices, it is important to study the properties behavior of these topological excitations during its movement on magnetic nanotracks, specially because in ferromagnetic materials they suffer a kind of magnus effect which tends to spell the skyrmion through the borders, preventing its transport throughout the nanotrack. We used micromagnetic simulations to study the dynamics of a skyrmion on a magnetic nanotrack induced by a spin polarized electric current. We considered thin magnetic nanotrack made of cobalt and platinum multilayers, whose magnetic state is perpendicular to the track plane and contain a single Néel-type Skyrmion. To describe this magnetic system, we used a Hamiltonian containing exchange, Dzyaloshinskii-Moriya, perpendicular magnetic anisotropy and dipole-dipole interactions. In our study we observed the well-known Skyrmion Hall effect and changes in the structure of the skyrmion when it approaches of the border. This alteration can be measured by determining the radius and the topological charge of the Skyrmion. Our simulation results show that both the radius and the topological charge decrease when it approaches of the border. Our study also demonstrates that the skyrmion-border interaction is repulsive, but there is a minimum distance from the border at which the interaction becomes attractive. If the skyrmion exceeds this critical position yc, it will be attracted and annihilated at the border of the nanotrack. We also performed simulations to obtain the limit value jc of the applied current density that the skyrmion can be transported along of the nanotrack without escaping from the side edge. From a technological point of view for possible applications in spintronic devices, the estimate of  jc  is of crucial importance.

scholarly journals Magnetic Skyrmion Generation by Reflective Spin Wave Focusing

2021 ◽  
Vol 9 ◽  
Author(s):  
Xianglong Yao ◽  
Zhenyu Wang ◽  
Menghua Deng ◽  
Z.-X. Li ◽  
Zhizhi Zhang ◽  
...  
Keyword(s):  
Topological Charge ◽  
Path Length ◽  
Focal Point ◽  
Spin Waves ◽  
Micromagnetic Simulations ◽  
Driving Field ◽  
Spintronic Devices ◽  
Theoretical Design ◽  
Frequency Independent ◽  
Magnetic Skyrmions

We propose a method to generate magnetic skyrmions by focusing spin waves totally reflected by a curved film edge. The edge contour is derived to be parabolic and frequency-independent based on the identical magnonic path length principle. We performed micromagnetic simulations to verify our theoretical design. Under proper conditions, the reflected spin waves first converge at the focal point with the enhanced intensity leading to the emergence of magnetic droplets, which are then converted to magnetic skyrmion accompanied by a change in the topological charge. We numerically obtain the phase diagram of skyrmion generation with respect to the amplitude and frequency of the driving field. Our finding would be helpful for the design of spintronic devices combining the advantage of skyrmionics and magnonics.

scholarly journals Neuro-Inspired Signal Processing in Ferromagnetic Nanofibers

Biomimetics ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 32
Author(s):  
Tomasz Blachowicz ◽  
Jacek Grzybowski ◽  
Pawel Steblinski ◽  
Andrea Ehrmann
Keyword(s):  
Data Processing ◽  
Data Storage ◽  
Domain Walls ◽  
Data Transfer ◽  
Synaptic Activity ◽  
Neuromorphic Computing ◽  
Rotating Magnetic Fields ◽  
Micromagnetic Simulations ◽  
Energy Consuming ◽  
Stochastic Data

Computers nowadays have different components for data storage and data processing, making data transfer between these units a bottleneck for computing speed. Therefore, so-called cognitive (or neuromorphic) computing approaches try combining both these tasks, as is done in the human brain, to make computing faster and less energy-consuming. One possible method to prepare new hardware solutions for neuromorphic computing is given by nanofiber networks as they can be prepared by diverse methods, from lithography to electrospinning. Here, we show results of micromagnetic simulations of three coupled semicircle fibers in which domain walls are excited by rotating magnetic fields (inputs), leading to different output signals that can be used for stochastic data processing, mimicking biological synaptic activity and thus being suitable as artificial synapses in artificial neural networks.

scholarly journals Electroweak axion string and superconductivity

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Yoshihiko Abe ◽  
Yu Hamada ◽  
Koichi Yoshioka
Keyword(s):  
Electric Current ◽  
Early Universe ◽  
Parameter Space ◽  
Cosmic String ◽  
Topological Charge ◽  
Attractive Force ◽  
Electroweak Scale ◽  
Large Current

Abstract We study the axion strings with the electroweak gauge flux in the DFSZ axion model and show that these strings, called the electroweak axion strings, can exhibit superconductivity without fermionic zeromodes. We construct three types of electroweak axion string solutions. Among them, the string with W-flux can be lightest in some parameter space, which leads to a stable superconducting cosmic string. We also show that a large electric current can flow along the string due to the Peccei-Quinn scale much higher than the electroweak scale. This large current induces a net attractive force between the axion strings with the same topological charge, which opens a novel possibility that the axion strings form Y-junctions in the early universe.

scholarly journals Micromagnetic Simulations of Fe and Ni Nanodot Arrays Surrounded by Magnetic or Non-Magnetic Matrices

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 349
Author(s):  
Devika Sudsom ◽  
Andrea Ehrmann
Keyword(s):  
Magnetic Materials ◽  
Data Storage ◽  
Magnetization Reversal ◽  
Hysteresis Loops ◽  
Object Oriented ◽  
Basic Research ◽  
Memory Systems ◽  
The Other ◽  
Micromagnetic Simulations ◽  
Nanodot Arrays

Combining clusters of magnetic materials with a matrix of other magnetic materials is very interesting for basic research because new, possibly technologically applicable magnetic properties or magnetization reversal processes may be found. Here we report on different arrays combining iron and nickel, for example, by surrounding circular nanodots of one material with a matrix of the other or by combining iron and nickel nanodots in air. Micromagnetic simulations were performed using the OOMMF (Object Oriented MicroMagnetic Framework). Our results show that magnetization reversal processes are strongly influenced by neighboring nanodots and the magnetic matrix by which the nanodots are surrounded, respectively, which becomes macroscopically visible by several steps along the slopes of the hysteresis loops. Such material combinations allow for preparing quaternary memory systems, and are thus highly relevant for applications in data storage and processing.

scholarly journals Dynamic transition of current-driven single-skyrmion motion in a room-temperature chiral-lattice magnet

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Licong Peng ◽  
Kosuke Karube ◽  
Yasujiro Taguchi ◽  
Naoto Nagaosa ◽  
Yoshinori Tokura ◽  
...  
Keyword(s):  
Electric Current ◽  
Motion Tracking ◽  
Room Temperature ◽  
Dynamic Transition ◽  
Spintronic Devices ◽  
Transmission Electron ◽  
Flow Motion ◽  
Lorentz Transmission Electron Microscopy ◽  
And Control

AbstractDriving and controlling single-skyrmion motion promises skyrmion-based spintronic applications. Recently progress has been made in moving skyrmionic bubbles in thin-film heterostructures and low-temperature chiral skyrmions in the FeGe helimagnet by electric current. Here, we report the motion tracking and control of a single skyrmion at room temperature in the chiral-lattice magnet Co9Zn9Mn2 using nanosecond current pulses. We have directly observed that the skyrmion Hall motion reverses its direction upon the reversal of skyrmion topological number using Lorentz transmission electron microscopy. Systematic measurements of the single-skyrmion trace as a function of electric current reveal a dynamic transition from the static pinned state to the linear flow motion via a creep event, in agreement with the theoretical prediction. We have clarified the role of skyrmion pinning and evaluated the intrinsic skyrmion Hall angle and the skyrmion velocity in the course of the dynamic transition. Our results pave a way to skyrmion applications in spintronic devices.

Spin transport in epitaxial Fe3O4/GaAs lateral structured device

2022 ◽  
Author(s):  
Zhaocong Huang ◽  
Wenqing Liu ◽  
Jian Liang ◽  
Qingjie Guo ◽  
Ya Zhai ◽  
...  
Keyword(s):  
Data Storage ◽  
Field Effect ◽  
Room Temperature ◽  
Field Effect Transistor ◽  
Spin Transport ◽  
Spintronic Devices ◽  
Spin Dependent Transport ◽  
Effect Transistor ◽  
Dependent Transport ◽  
Further Development

Abstract Research in the spintronics community has been intensively stimulated by the proposal of the spin field-effect transistor (SFET), which has the potential for combining the data storage and process in a single device. Here we report the spin dependent transport on a Fe3O4/GaAs based lateral structured device. Parallel and antiparallel states of two Fe3O4 electrodes are achieved. A clear MR loop shows the perfect butterfly shape at room temperature, of which the intensity decreases with the reducing current, showing the strong bias-dependence. Understanding the spin dependent transport properties in this architecture has strong implication in further development of the spintronic devices for room-temperature SFET.

Shape Factors and Feasibility of Sheet Metal Hydroformed Components

2015 ◽  
Vol 651-653 ◽  
pp. 1134-1139
Author(s):  
Teresa Primo ◽  
Gabriele Papadia ◽  
Antonio del Prete
Keyword(s):  
Shape Factor ◽  
Point Of View ◽  
Element Analysis ◽  
Shape Factors ◽  
Limit Values ◽  
Limit Value ◽  
Experimental Campaign ◽  
Correct Calculation ◽  
Proper Comparison ◽  
Definition Of

The authors have investigated, in other paper, the problem related to the definition of a “set of shape factors” in order to declare the feasibility of a product through sheet hydroforming. In particular the defined shape factors are three different a-dimensional coefficients by which it is possible to declare the feasibility of a product through the calculation, in different sections, of the three previous shape factors. The robustness of this methodology is related to the correct calculation of the “limit value” of each shape factor. In fact the feasibility is reached if, in any section, the calculated shape factors are higher than their respective limit values. In this paper the authors have performed an extensive numerical and experimental campaign, taking into account a different geometry respect to that of the first paper, in order to: re-calculate the limit value for each shape factor and, then, verify the correctness of the limit values exposed in the previous first paper. The numerical campaign has been used, after the evaluation of the accuracy of the numerical model, in order to study the feasibility of the product without engaging the hydroforming machine. Finite Element Analysis (FEA) has been extensively used in order to investigate and define each shape factor with a proper comparison to the macro feasibility of the chosen component geometry. The limit values that have been calculated by the authors in this paper are slightly different from those calculated in the first paper. From this point of view it is possible that, although the shape factors are a-dimensional coefficients, they are affected by different choices of the users as, for example, the dimensions of the initial blank. Anyway, the small differences in the shape factors limit values do not adversely affect the use of the shape factors in order to predict the feasibility of the product.

scholarly journals Theoretical Study of Field-Free Switching in PMA-MTJ Using Combined Injection of STT and SOT Currents

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1345
Author(s):  
Shaik Wasef ◽  
Hossein Fariborzi
Keyword(s):  
Critical Current ◽  
Theoretical Study ◽  
Tunnel Junctions ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Spin Orbit ◽  
Micromagnetic Simulations ◽  
Spintronic Devices ◽  
Current Densities ◽  
The Relationship

Field-free switching in perpendicular magnetic tunnel junctions (P-MTJs) can be achieved by combined injection of spin-transfer torque (STT) and spin-orbit torque (SOT) currents. In this paper, we derived the relationship between the STT and SOT critical current densities under combined injection. We included the damping–like torque (DLT) and field-like torque (FLT) components of both the STT and SOT. The results were derived when the ratio of the FLT to the DLT component of the SOT was positive. We observed that the relationship between the critical SOT and STT current densities depended on the damping constant and the magnitude of the FLT component of the STT and the SOT current. We also noted that, unlike the FLT component of SOT, the magnitude and sign of the FLT component of STT did not have a significant effect on the STT and SOT current densities required for switching. The derived results agreed well with micromagnetic simulations. The results of this work can serve as a guideline to model and develop spintronic devices using a combined injection of STT and SOT currents.

scholarly journals Implementation and Analysis of Enhanced Obfuscation Technique for Data Security

2019 ◽  
Vol 8 (3) ◽  
pp. 6107-6115
Keyword(s):  
Information Security ◽  
Data Storage ◽  
Computation Time ◽  
Point Of View ◽  
Malicious Attacks ◽  
Security Systems ◽  
Avalanche Effect ◽  
Processing Power ◽  
Fast Development ◽  
Obfuscation Technique

With the fast development of digital exchange of data in an electronic way, data and information security are becoming more important in both transmission and data storage. Cryptography is used as a solution which plays an important role in data and information security systems against malicious attacks. The encryption technique is used to provide confidentiality to the data during transmission because security threats are more on data during transmission than data at rest. One can also use encryption to secure user’s data at data storage (i.e., data at rest). But an encryption algorithm consumes a more amount of computing resources such as processing power, memory and computation time. Obfuscation technique is a very lightweight technique that comes into a picture to protect the data at storage from malicious attacks. There are many obfuscation techniques are available to ensure the confidentiality of the data. In this paper, an obfuscation technique has been proposed and implemented which uses a 128-bit key to improve the security of the data. The experimental results show that the time taken for obfuscation and de-obfuscation is less and also from the security point of view it provides high avalanche effect

scholarly journals Four Subjects in Solar Physics from the Point of View of the Electric Current Approach

2020 ◽  
pp. 33-45
Author(s):  
Syun-Ichi Akasofu
Keyword(s):  
Solar Wind ◽  
Electric Current ◽  
Solar Flares ◽  
Solar Physics ◽  
Current Approach ◽  
Point Of View ◽  
Coronal Temperature ◽  
The Past ◽  
Electromagnetic Processes ◽  
Difficult Subjects

Four major subjects in solar physics, the heating of the corona, the cause of the solar wind, the formation of sunspots and the cause of solar flares, are discussed on the basis of the electric current approach, a sequence of processes consisting of power supply(dynamo), transmission (currents/circuits) and dissipation(high coronal temperature, solar wind, sunspots and solar flares).This is because the four subjects have hardly been considered in terms of the electric current approach in the past, in spite of the fact that these subjects are various manifestations of electromagnetic processes. It is shown that this approach provides a new systematic way of considering each subject; (1) the long-standing issue of the coronal temperature, (2)the long-standing problem on the cause of the solar wind, (3)the presence of single spots(forgotten or dismissed in the past) and its relation to unipolar magnetic regions and (4) the crucial power/energy source and subsequent explosive processes of solar flares. The four subjects are obviously extremely complicated and difficult subjects, but it is hoped that the electric current approach might provide a new insight in considering the four subjects.

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