scholarly journals Micromagnetic Simulation of Round Ferromagnetic Nanodots with Varying Roughness and Symmetry

2021 ◽  
Vol 6 (2) ◽  
pp. 19
Author(s):  
Pia Steinmetz ◽  
Andrea Ehrmann
Keyword(s):  
Data Storage ◽  
Magnetization Reversal ◽  
Hysteresis Loops ◽  
Basic Research ◽  
Magnetic Data ◽  
Field Orientation ◽  
Thin Ring ◽  
Production Technologies ◽  
Magnetic States ◽  
The Impact

Magnetic nanodots are of high interest for basic research due to their broad spectrum of possible magnetic states and magnetization reversal processes. Besides, they are of technological interest since they can be applied in magnetic data storage, especially if vortex states occur in closed dots or open rings. While producing such nanorings and nanodots from diverse magnetic materials by lithographic techniques is quite common nowadays, these production technologies are naturally prone to small deviations of the borders of these nanoparticles. Here we investigate the influence of well-defined angular-dependent roughness of the edges, created by building the nanoparticles from small cubes, on the resulting hysteresis loops and magnetization reversal processes in five different round nanodots with varying open areas, from a thin ring to a closed nanodot. By varying the orientation of the external magnetic field, the impact of the angle-dependent roughness can be estimated. Especially for the thinnest ring, significant dependence of the transverse magnetization component on the field orientation can be found.

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 Magnetization Reversal Process and Magnetostatic Interactions in Fe56Co44/SiO2/Fe3O4 Core/Shell Ferromagnetic Nanowires with Non-Magnetic Interlayer

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2282
Author(s):  
Javier García ◽  
Alejandro M. Manterola ◽  
Miguel Méndez ◽  
Jose Angel Fernández-Roldán ◽  
Víctor Vega ◽  
...  
Keyword(s):  
Data Storage ◽  
Magnetization Reversal ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Hysteresis Loops ◽  
Magnetic Data ◽  
Core Shell ◽  
The Core ◽  
Shell Nanostructures ◽  
Magnetostatic Interactions

Nowadays, numerous works regarding nanowires or nanotubes are being published, studying different combinations of materials or geometries with single or multiple layers. However, works, where both nanotube and nanowires are forming complex structures, are scarcer due to the underlying difficulties that their fabrication and characterization entail. Among the specific applications for these nanostructures that can be used in sensing or high-density magnetic data storage devices, there are the fields of photonics or spintronics. To achieve further improvements in these research fields, a complete understanding of the magnetic properties exhibited by these nanostructures is needed, including their magnetization reversal processes and control of the magnetic domain walls. In order to gain a deeper insight into this topic, complex systems are being fabricated by altering their dimensions or composition. In this work, a successful process flow for the additive fabrication of core/shell nanowires arrays is developed. The core/shell nanostructures fabricated here consist of a magnetic nanowire nucleus (Fe56Co44), grown by electrodeposition and coated by a non-magnetic SiO2 layer coaxially surrounded by a magnetic Fe3O4 nanotubular coating both fabricated by means of the Atomic Layer Deposition (ALD) technique. Moreover, the magnetization reversal processes of these coaxial nanostructures and the magnetostatic interactions between the two magnetic components are investigated by means of standard magnetometry and First Order Reversal Curve methodology. From this study, a two-step magnetization reversal of the core/shell bimagnetic nanostructure is inferred, which is also corroborated by the hysteresis loops of individual core/shell nanostructures measured by Kerr effect-based magnetometer.

scholarly journals Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie Structures

2020 ◽  
Vol 5 (1) ◽  
pp. 5 ◽  
Author(s):  
Devika Sudsom ◽  
Irén Juhász Junger ◽  
Christoph Döpke ◽  
Tomasz Blachowicz ◽  
Lothar Hahn ◽  
...  
Keyword(s):  
Data Storage ◽  
Vortex Formation ◽  
Basic Research ◽  
Micromagnetic Simulation ◽  
Magnetic Vortex ◽  
Magnetic Memory ◽  
Thick Sample ◽  
Field Orientation ◽  
Micromagnetic Simulations ◽  
Bow Tie

Magnetic vortex structures are of high technological relevance due to their possible application in magnetic memory. Moreover, investigating magnetization reversal via vortex formation is an important topic in basic research. Typically, such vortices are only investigated in homogeneous magnetic materials of diverse shapes. Here, we report for the first time on micromagnetic simulation of vortex formation in magnetic bow-tie nanostructures, comprising alternating parts from iron and permalloy, investigated for two different thicknesses and under different angles of the external magnetic field. While no vortex was found in pure permalloy square, nanoparticles of the dimensions investigated in this study and in case of iron only a relatively thick sample allowed for vortex formation, different numbers of vortices and antivortices were found in the bow-tie structures prepared from both materials, depending on the angular field orientation and the sample thickness. By stabilizing more than one vortex in a confined nanostructure, it is possible to store more than one bit of information in it. Our micromagnetic simulations reveal that such bi-material structures are highly relevant not only for basic research, but also for data storage applications.

scholarly journals Investigation on the Effect of Femtosecond Laser Induced Spin Transfer Torque of GdFeCo Alloy

2021 ◽  
Vol 11 (14) ◽  
pp. 6501
Author(s):  
Haozhe Huang ◽  
Haiwei Wang ◽  
Zhihao Zeng ◽  
Rongyao Wang ◽  
Xinyu Zhang ◽  
...  
Keyword(s):  
Data Storage ◽  
Current Density ◽  
Magnetization Reversal ◽  
Spin Current ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Magnetic Data ◽  
Magnetization Switching ◽  
Switching Speed ◽  
Novel Approach

All-optical magnetic switching (AOS) provides a novel approach to improve writing ability and energy efficiency compared to those utilized in the mainstream magnetic data storage products. Rare earth-transition metals (RE-TM) exhibit extremely fast magnetization switching induced by one single incident linearly polarized laser pulse; however, the mechanism is still ambiguous. Here, we show by atomistic spin simulation that the laser induced spin transfer torque dominates the magnetization reversal of Fe sublattice in Gd25Fe75 alloy, and that the switching speed of Gd25Fe75 alloy is relevant to the amount of spin current. This implies that a possible helicity independent mechanism underlies the RE-TM alloy AOS process. We also find that the greater the spin current density the faster the magnetization switching, and the time magnetization reversal of Gd and Fe takes is also affected by the spin current density.

scholarly journals Multiferroicity and skyrmions carrying electric polarization in GaV4S8

2015 ◽  
Vol 1 (10) ◽  
pp. e1500916 ◽  
Author(s):  
Eugen Ruff ◽  
Sebastian Widmann ◽  
Peter Lunkenheimer ◽  
Vladimir Tsurkan ◽  
Sandor Bordács ◽  
...  
Keyword(s):  
Data Storage ◽  
Electric Fields ◽  
Magnetic Phase Diagram ◽  
Basic Research ◽  
Electric Polarization ◽  
Spatial Modulation ◽  
Magnetic Data ◽  
Orbital Ordering ◽  
Microscopic Mechanism ◽  
Polar Crystal

Skyrmions are whirl-like topological spin objects with high potential for future magnetic data storage. A fundamental question that is relevant to both basic research and application is whether ferroelectric (FE) polarization can be associated with skyrmions’ magnetic texture and whether these objects can be manipulated by electric fields. We study the interplay between magnetism and electric polarization in the lacunar spinel GaV4S8, which undergoes a structural transition associated with orbital ordering at 44 K and reveals a complex magnetic phase diagram below 13 K, including ferromagnetic, cycloidal, and Néel-type skyrmion lattice (SkL) phases. We found that the orbitally ordered phase of GaV4S8 is FE with a sizable polarization of ~1 μC/cm2. Moreover, we observed spin-driven excess polarizations in all magnetic phases; hence, GaV4S8 hosts three different multiferroic phases with coexisting polar and magnetic order. These include the SkL phase, where we predict a strong spatial modulation of FE polarization close to the skyrmion cores. By taking into account the crystal symmetry and spin patterns of the magnetically ordered phases, we identify exchange striction as the main microscopic mechanism behind the spin-driven FE polarization in each multiferroic phase. Because GaV4S8 is unique among known SkL host materials owing to its polar crystal structure and the observed strong magnetoelectric effect, this study is an important step toward the nondissipative electric field control of skyrmions.

scholarly journals Effect of Sharp Diameter Geometrical Modulation on the Magnetization Reversal of bi-Segmented FeNi Nanowires

2018 ◽  
Author(s):  
Miguel Méndez ◽  
Víctor Vega ◽  
Silvia González ◽  
Rafael Caballero-Flores ◽  
Javier García ◽  
...  
Keyword(s):  
Data Storage ◽  
Magnetization Reversal ◽  
Magnetic Nanostructures ◽  
Magnetic Behavior ◽  
Magnetic Data ◽  
Micromagnetic Simulations ◽  
Precise Control ◽  
Different Types ◽  
Magnetic Decoupling ◽  
Different Diameters

Controlling functional properties of matter and combine them for engineering a functional device is nowadays a common direction of scientific community. For instance, heterogeneous magnetic nanostructures can make use of different types of geometrical and compositional modulations to achieve the control of the magnetization reversal along with the nano-entities and thus enabling the fabrication of spintronic, magnetic data storage and sensing devices, among others. In this work, diameter modulated FeNi nanowires are fabricated paying special effort to obtain sharp transition regions between two segments of different diameters (from about 450 nm to 120 nm), enabling precise control over the magnetic behavior of the sample. Micromagnetic simulations performed on single bi-segmented nanowires predict a double step magnetization reversal where the wide segment magnetization switches near 200 Oe through a vortex domain wall, while at 500 Oe the magnetization of the narrow one is reversed through a corkscrew like mechanism. Finally, these results are confirmed with magneto-optic Kerr effect measurements at the transition of isolated bi-segmented nanowires. Furthermore, macroscopic vibrating sample magnetometry is used to demonstrate that the magnetic decoupling of nanowire segments is the main phenomenon occurring over the entire fabricated nanowires.

scholarly journals Effect of Sharp Diameter Geometrical Modulation on the Magnetization Reversal of Bi-Segmented FeNi Nanowires

Nanomaterials ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 595 ◽  
Author(s):  
Miguel Méndez ◽  
Víctor Vega ◽  
Silvia González ◽  
Rafael Caballero-Flores ◽  
Javier García ◽  
...  
Keyword(s):  
Data Storage ◽  
Magnetization Reversal ◽  
Magnetic Nanostructures ◽  
Magnetic Behavior ◽  
Magnetic Data ◽  
Micromagnetic Simulations ◽  
Precise Control ◽  
Different Types ◽  
Magnetic Decoupling ◽  
Different Diameters

Controlling functional properties of matter and combining them for engineering a functional device is, nowadays, a common direction of the scientific community. For instance, heterogeneous magnetic nanostructures can make use of different types of geometrical and compositional modulations to achieve the control of the magnetization reversal along with the nano-entities and, thus, enable the fabrication of spintronic, magnetic data storage, and sensing devices, among others. In this work, diameter-modulated FeNi nanowires are fabricated paying special effort to obtain sharp transition regions between two segments of different diameters (from about 450 nm to 120 nm), enabling precise control over the magnetic behavior of the sample. Micromagnetic simulations performed on single bi-segmented nanowires predict a double step magnetization reversal where the wide segment magnetization switches near 16 kA/m through a vortex domain wall, while at 40 kA/m the magnetization of the narrow segment is reversed through a corkscrew-like mechanism. Finally, these results are confirmed with magneto-optic Kerr effect measurements at the transition of isolated bi-segmented nanowires. Furthermore, macroscopic vibrating sample magnetometry is used to demonstrate that the magnetic decoupling of nanowire segments is the main phenomenon occurring over the entire fabricated nanowires.

scholarly journals Narrow Segment Driven Multistep Magnetization Reversal Process in Sharp Diameter Modulated Fe67Co33 Nanowires

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3077
Author(s):  
Javier García ◽  
Jose A. Fernández-Roldán ◽  
Roque González ◽  
Miguel Méndez ◽  
Cristina Bran ◽  
...  
Keyword(s):  
Data Storage ◽  
Magnetization Reversal ◽  
Domain Walls ◽  
Nanowire Array ◽  
Magnetic Hysteresis ◽  
Magnetic Domain ◽  
Hysteresis Loops ◽  
Magnetic Behavior ◽  
Magnetic Nanomaterials ◽  
Magnetic Nanowires

Magnetic nanomaterials are of great interest due to their potential use in data storage, biotechnology, or spintronic based devices, among others. The control of magnetism at such scale entails complexing the nanostructures by tuning their composition, shape, sizes, or even several of these properties at the same time, in order to search for new phenomena or optimize their performance. An interesting pathway to affect the dynamics of the magnetization reversal in ferromagnetic nanostructures is to introduce geometrical modulations to act as nucleation or pinning centers for the magnetic domain walls. Considering the case of 3D magnetic nanowires, the modulation of the diameter across their length can produce such effect as long as the segment diameter transition is sharp enough. In this work, diameter modulated Fe67Co33 ferromagnetic nanowires have been grown into the prepatterned diameter modulated nanopores of anodized Al2O3 membranes. Their morphological and compositional characterization was carried out by electron-based microscopy, while their magnetic behavior has been measured on both the nanowire array as well as for individual bisegmented nanowires after being released from the alumina template. The magnetic hysteresis loops, together with the evaluation of First Order Reversal Curve diagrams, point out that the magnetization reversal of the bisegmented FeCo nanowires is carried out in two steps. These two stages are interpreted by micromagnetic modeling, where a shell of the wide segment reverses its magnetization first, followed by the reversal of its core together with the narrow segment of the nanowire at once.

scholarly journals Detecting Convergence Trends among EU Universities

Economies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 42
Author(s):  
Maria Adamakou ◽  
Dimitris Kallioras ◽  
George Petrakos
Keyword(s):  
Methodological Approach ◽  
Basic Research ◽  
Valuable Insight ◽  
Traditional Role ◽  
University Ranking ◽  
Convergence Clubs ◽  
Development Processes ◽  
The Impact ◽  
The Empirical Analysis ◽  
Insight Into

Universities are emerging growth determinants. This is so as, in addition to the fulfillment of their traditional role in teaching and (basic) research, universities, as aptly described within the helix framework, are expected to engage in regional development processes. The paper aims to detect trends of convergence among EU universities in terms of performance. To the best of our knowledge, this topic has not hitherto been examined. The empirical analysis of the paper covers the period 2014–2021, utilizes data obtained from URAP (University Ranking by Academic Performance), and employs the methodological approach of convergence clubs. The findings of the paper provide valuable insight into both theory and policy-making. We conclude that despite the unification of EU educational space, trends of divergence among EU universities are still present, and notable divisions still remain. Consequently, this indicates that the impact of EU universities on the formation of spatial disparities across EU space is not neutral.

scholarly journals Nanostructured ZnFe2O4: An Exotic Energy Material

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1286
Author(s):  
Murtaza Bohra ◽  
Vidya Alman ◽  
Rémi Arras
Keyword(s):  
Data Storage ◽  
Smart Materials ◽  
Energy Demand ◽  
Ceramic Materials ◽  
Magnetic Data ◽  
Processing Route ◽  
Energy Storage Devices ◽  
Storage Devices ◽  
Reduced Toxicity ◽  
Cation Arrangement

More people, more cities; the energy demand increases in consequence and much of that will rely on next-generation smart materials. Zn-ferrites (ZnFe2O4) are nonconventional ceramic materials on account of their unique properties, such as chemical and thermal stability and the reduced toxicity of Zn over other metals. Furthermore, the remarkable cation inversion behavior in nanostructured ZnFe2O4 extensively cast-off in the high-density magnetic data storage, 5G mobile communication, energy storage devices like Li-ion batteries, supercapacitors, and water splitting for hydrogen production, among others. Here, we review how aforesaid properties can be easily tuned in various ZnFe2O4 nanostructures depending on the choice, amount, and oxidation state of metal ions, the specific features of cation arrangement in the crystal lattice and the processing route used for the fabrication.

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