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Journal articles on the topic 'Magnetické vortexy'

Author: Grafiati

Published: 4 June 2021

Last updated: 9 February 2022

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1

Mintairov, Alexander, Dmitrii Lebedev, Alexei Vlasov, Andrey Bogdanov, Shahab Ramezanpour, and Steven Blundell. "Fractional Charge States in the Magneto-Photoluminescence Spectra of Single-Electron InP/GaInP2 Quantum Dots." Nanomaterials 11, no. 2 (February 16, 2021): 493. http://dx.doi.org/10.3390/nano11020493.

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We used photoluminescence spectra of single electron quasi-two-dimensional InP/GaInP2 islands having Wigner-Seitz radius ~4 to measure the magnetic-field dispersion of the lowest s, p, and d single-particle states in the range 0–10 T. The measured dispersion revealed up to a nine-fold reduction of the cyclotron frequency, indicating the formation of nano-superconducting anyon or magneto-electron (em) states, in which the corresponding number of magnetic-flux-quanta vortexes and fractional charge were self-generated. We observed a linear increase in the number of vortexes versus the island size, which corresponded to a critical vortex radius equal to the Bohr radius and closed-packed topological vortex arrangements. Our observation explains the microscopic mechanism of vortex attachment in composite fermion theory of the fractional quantum Hall effect, allows its description in terms of self-localization of ems and represents progress towards the goal of engineering anyon properties for fault-tolerant topological quantum gates.

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2

Pylypovskyi, O. V., D. D. Sheka, V. P. Kravchuk, Yu B. Gaididei, and F. G. Mertens. "Mechanism of Fast Axially Symmetric Reversal of Magnetic Vortex Core." Ukrainian Journal of Physics 58, no. 6 (June 2013): 596–603. http://dx.doi.org/10.15407/ujpe58.06.0596.

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3

Xie, Hui, Mengmeng Sun, Xinjian Fan, Zhihua Lin, Weinan Chen, Lei Wang, Lixin Dong, and Qiang He. "Reconfigurable magnetic microrobot swarm: Multimode transformation, locomotion, and manipulation." Science Robotics 4, no. 28 (March 20, 2019): eaav8006. http://dx.doi.org/10.1126/scirobotics.aav8006.

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Swimming microrobots that are energized by external magnetic fields exhibit a variety of intriguing collective behaviors, ranging from dynamic self-organization to coherent motion; however, achieving multiple, desired collective modes within one colloidal system to emulate high environmental adaptability and enhanced tasking capabilities of natural swarms is challenging. Here, we present a strategy that uses alternating magnetic fields to program hematite colloidal particles into liquid, chain, vortex, and ribbon-like microrobotic swarms and enables fast and reversible transformations between them. The chain is characterized by passing through confined narrow channels, and the herring school–like ribbon procession is capable of large-area synchronized manipulation, whereas the colony-like vortex can aggregate at a high density toward coordinated handling of heavy loads. Using the developed discrete particle simulation methods, we investigated generation mechanisms of these four swarms, as well as the “tank-treading” motion of the chain and vortex merging. In addition, the swarms can be programmed to steer in any direction with excellent maneuverability, and the vortex’s chirality can be rapidly switched with high pattern stability. This reconfigurable microrobot swarm can provide versatile collective modes to address environmental variations or multitasking requirements; it has potential to investigate fundamentals in living systems and to serve as a functional bio-microrobot system for biomedicine.

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4

Watson, J. L. S., and Z. Li. "Vortex magnetic separation." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 211, no. 1 (February 1, 1997): 31–42. http://dx.doi.org/10.1243/0954408971529520.

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Vortex magnetic separation (VMS) is a new technique (1-3) which can not only greatly increase selectivity of high gradient magnetic separation but can also provide a much higher material throughput because high slurry velocity is used. This technique will have a wide range of applications in fields as diverse as mineral processing, biochemical engineering, sewage and wastewater treatment and industrial effluent treatment. At present in high gradient magnetic separation (HGMS) low Reynolds numbers (with respect to the wire diameter) are usually used and the magnetic product is captured on the upstream side of the wire matrix which results in a serious mechanical entrainment problem that is very detrimental to the purity of the magnetic fraction and to the reduction of the quantity of non-magnetic fraction (4). Vortex magnetic separation runs at moderate Reynolds number ( Re = 6–40) which leads to the formation of vortex flow in the neighbourhood of the matrix. Magnetic particles in the slurry are first concentrated in the boundary layer flow around the matrix and then brought into the magnetically attractive area on the matrix downstream side. The magnetic deposit on the downstream side of the matrix does not suffer the direct collisions with non-magnetic particles in the slurry, so the quality of the magnetic product is drastically improved. As will be described below, a new invention has been made with regard to the VMS matrix which allows capture to take place on both the upstream and downstream sides of the matrix without mechanical entrainment. This paper reviews experimental and theoretical work on the mechanisms involved in vortex magnetic separation.

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5

Antos, Roman, YoshiChika Otani, and Junya Shibata. "Magnetic Vortex Dynamics." Journal of the Physical Society of Japan 77, no. 3 (March 15, 2008): 031004. http://dx.doi.org/10.1143/jpsj.77.031004.

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6

Garcia, F., J. P. Sinnecker, E. R. P. Novais, and A. P. Guimarães. "Magnetic vortex echoes." Journal of Applied Physics 112, no. 11 (December 2012): 113911. http://dx.doi.org/10.1063/1.4768446.

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7

Hrkac, Gino, Paul S. Keatley, Matthew T. Bryan, and Keith Butler. "Magnetic vortex oscillators." Journal of Physics D: Applied Physics 48, no. 45 (October 6, 2015): 453001. http://dx.doi.org/10.1088/0022-3727/48/45/453001.

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8

Guervilly, Céline, David W. Hughes, and Chris A. Jones. "Large-scale-vortex dynamos in planar rotating convection." Journal of Fluid Mechanics 815 (February 20, 2017): 333–60. http://dx.doi.org/10.1017/jfm.2017.56.

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Several recent studies have demonstrated how large-scale vortices may arise spontaneously in rotating planar convection. Here, we examine the dynamo properties of such flows in rotating Boussinesq convection. For moderate values of the magnetic Reynolds number ($100\lesssim Rm\lesssim 550$, with $Rm$ based on the box depth and the convective velocity), a large-scale (i.e. system-size) magnetic field is generated. The amplitude of the magnetic energy oscillates in time, nearly out of phase with the oscillating amplitude of the large-scale vortex. The large-scale vortex is disrupted once the magnetic field reaches a critical strength, showing that these oscillations are of magnetic origin. The dynamo mechanism relies on those components of the flow that have length scales lying between that of the large-scale vortex and the typical convective cell size; smaller-scale flows are not required. The large-scale vortex plays a crucial role in the magnetic induction despite being essentially two-dimensional; we thus refer to this dynamo as a large-scale-vortex dynamo. For larger magnetic Reynolds numbers, the dynamo is small scale, with a magnetic energy spectrum that peaks at the scale of the convective cells. In this case, the small-scale magnetic field continuously suppresses the large-scale vortex by disrupting the correlations between the convective velocities that allow it to form. The suppression of the large-scale vortex at high $Rm$ therefore probably limits the relevance of the large-scale-vortex dynamo to astrophysical objects with moderate values of $Rm$, such as planets. In this context, the ability of the large-scale-vortex dynamo to operate at low magnetic Prandtl numbers is of great interest.

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9

Guslienko, K. Yu. "Magnetic Vortex State Stability, Reversal and Dynamics in Restricted Geometries." Journal of Nanoscience and Nanotechnology 8, no. 6 (June 1, 2008): 2745–60. http://dx.doi.org/10.1166/jnn.2008.18305.

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Magnetic vortices are typically the ground states in geometrically confined ferromagnets with small magnetocrystalline anisotropy. In this article I review static and dynamic properties of the magnetic vortex state in small particles with nanoscale thickness and sub-micron and micron lateral sizes (magnetic dots). Magnetic dots made of soft magnetic material shaped as flat circular and elliptic cylinders are considered. Such mesoscopic dots undergo magnetization reversal through successive nucleation, displacement and annihilation of magnetic vortices. The reversal process depends on the stability of different possible zero-field magnetization configurations with respect to the dot geometrical parameters and application of an external magnetic field. The interdot magnetostatic interaction plays an important role in magnetization reversal for dot arrays with a small dot-to-dot distance, leading to decreases in the vortex nucleation and annihilation fields. Magnetic vortices reveal rich, non-trivial dynamical properties due to existance of the vortex core bearing topological charges. The vortex ground state magnetization distribution leads to a considerable modification of the nature of spin excitations in comparison to those in the uniformly magnetized state. A magnetic vortex confined in a magnetically soft ferromagnet with micron-sized lateral dimensions possesses a characteristic dynamic excitation known as a translational mode that corresponds to spiral-like precession of the vortex core around its equilibrium position. The translation motions of coupled vortices are considered. There are, above the vortex translation mode eigenfrequencies, several dynamic magnetization eigenmodes localized outside the vortex core whose frequencies are determined principally by dynamic demagnetizing fields appearing due to restricted dot geometry. The vortex excitation modes are classified as translation modes and radially or azimuthally symmetric spin waves over the vortex ground state. Studying the spin eigenmodes in such systems provides valuable information to relate the particle dynamical response to geometrical parameters. Unresolved problems are identified to attract attention of researchers working in the area of nanomagnetism.

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10

REED, D. S., N. C. YEH, W. JIANG, U. KRIPLANI, M. KONCZYKOWSKI, and F. HOLTZBERG. "ANISOTROPIC VORTEX DYNAMICS AND PHASE DIAGRAM OF YBa2Cu3O7 SINGLE CRYSTALS WITH CANTED COLUMNAR DEFECTS." International Journal of Modern Physics B 10, no. 22 (October 10, 1996): 2723–43. http://dx.doi.org/10.1142/s0217979296001215.

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The anisotropic vortex dynamics and phase diagram are determined for a YBa 2 Cu 3 O 7 single crystal with columnar defects oriented at ±7.5° relative to the crystalline c-axis. A second-order splayed-glass to vortex-liquid transition is manifested for magnetic fields nearly parallel to the columns via the critical scaling of vortex AC and DC transport properties. In contrast, for magnetic fields aligned close to the ab-plane, an XY-like vortex-glass transition prevails. For magnetic fields at intermediate angles, there is no evidence of any vortex phase transition, and the vortex dynamics is described in terms of the thermally activated flux flow model.

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11

SHANG, XINLE, PENGMING ZHANG, and WEI ZUO. "THE TOPOLOGICAL STRUCTURE OF SINGLE VORTEX IN THE FF STATE." Modern Physics Letters B 25, no. 26 (October 20, 2011): 2041–51. http://dx.doi.org/10.1142/s0217984911027261.

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In this paper, we study the coexistence of the vortex and the FF state by using the generalized Ginzburg–Landau (GL) functional with the applied magnetic field, and obtain the numeric solutions. Furthermore, we investigate the topological structure of the vortex and find that the property of vortices relies heavily on the modulation q along z-axis. There is no topological vortex when q < qp, and the value [Formula: see text] is more favorable for the topological vortex. Moreover the magnetic field at the core of the vortex is obtained for the topological vortex.

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12

Gorkavenko, Volodymyr M., Iryna V. Ivanchenko, and Yurii A. Sitenko. "Induced vacuum current and magnetic field in the background of a vortex." International Journal of Modern Physics A 31, no. 06 (February 24, 2016): 1650017. http://dx.doi.org/10.1142/s0217751x16500172.

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A topological defect in the form of the Abrikosov–Nielsen–Olesen vortex is considered as a gauge-flux-carrying tube that is impenetrable for quantum matter. Charged scalar matter field is quantized in the vortex background with the perfectly reflecting (Dirichlet) boundary condition imposed at the side surface of the vortex. We show that a current circulating around the vortex and a magnetic field directed along the vortex are induced in the vacuum, if the Compton wavelength of the matter field exceeds considerably the transverse size of the vortex. The vacuum current and magnetic field are periodic in the value of the gauge flux of the vortex, providing a quantum-field-theoretical manifestation of the Aharonov–Bohm effect. The total flux of the induced vacuum magnetic field attains notable finite values even for the Compton wavelength of the matter field exceeding the transverse size of the vortex by just three orders of magnitude.

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13

Adhikari, Prabal, and Jaehong Choi. "Magnetic vortices in the Abelian Higgs model with derivative interactions." International Journal of Modern Physics A 33, no. 36 (December 30, 2018): 1850215. http://dx.doi.org/10.1142/s0217751x18502159.

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We study the properties of a single magnetic vortex and magnetic vortex lattices in a generalization of the Abelian Higgs model containing the simplest derivative interaction that preserves the [Formula: see text] gauge symmetry of the original model. The paper is motivated by the study of finite isospin chiral perturbation theory in a uniform, external magnetic field: since pions are Goldstone bosons of QCD (due to chiral symmetry breaking by the QCD vacuum), they interact through momentum-dependent terms. We find the asymptotic properties of single vortex solutions and compare them to the well-known solutions of the standard Abelian Higgs model. Furthermore, we study the vortex lattice solutions near the upper critical field using the method of “successive approximations,” which was originally used by Abrikosov in his seminal paper on type-II superconductors. We find the vortex lattice structure, which remains hexagonal as in the standard Abelian Higgs model, and condensation energy of the vortex lattices relative to the normal vacuum (in a uniform magnetic field).

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14

Stebliy, Maxim E., Alexander G. Kolesnikov, Alexey V. Ognev, Alexander S. Samardak, and Ludmila A. Chebotkevich. "Manipulation of magnetic vortex parameters in disk-on-disk nanostructures with various geometry." Beilstein Journal of Nanotechnology 6 (March 10, 2015): 697–703. http://dx.doi.org/10.3762/bjnano.6.70.

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Magnetic nanostructures in the form of a sandwich consisting of two permalloy (Py) disks with diameters of 600 and 200 nm separated by a nonmagnetic interlayer are studied. Magnetization reversal of the disk-on-disk nanostructures depends on the distance between centers of the small and big disks and on orientation of an external magnetic field applied during measurements. It is found that manipulation of the magnetic vortex chirality and the trajectory of the vortex core in the big disk is only possible in asymmetric nanostructures. Experimentally studied peculiarities of a motion path of the vortex core and vortex parameters by the magneto-optical Kerr effect (MOKE) magnetometer are supported by the magnetic force microscopy imaging and micromagnetic simulations.

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15

Sudsom, Devika, Irén Juhász Junger, Christoph Döpke, Tomasz Blachowicz, Lothar Hahn, and Andrea Ehrmann. "Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie Structures." Condensed Matter 5, no. 1 (January 12, 2020): 5. http://dx.doi.org/10.3390/condmat5010005.

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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.

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16

Geng, Liwei D., and Yongmei M. Jin. "Magnetic vortex racetrack memory." Journal of Magnetism and Magnetic Materials 423 (February 2017): 84–89. http://dx.doi.org/10.1016/j.jmmm.2016.09.062.

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17

Barros, Manuel, José L. Cabrerizo, Manuel Fernández, and Alfonso Romero. "Magnetic vortex filament flows." Journal of Mathematical Physics 48, no. 8 (August 2007): 082904. http://dx.doi.org/10.1063/1.2767535.

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18

Li, Z., and J. H. P. Watson. "Vortex magnetic separation (VMS)." IEEE Transactions on Magnetics 30, no. 6 (1994): 4662–64. http://dx.doi.org/10.1109/20.334182.

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19

Shelyag, S., V. Fedun, F. P. Keenan, R. Erdélyi, and M. Mathioudakis. "Photospheric magnetic vortex structures." Annales Geophysicae 29, no. 5 (May 23, 2011): 883–87. http://dx.doi.org/10.5194/angeo-29-883-2011.

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Abstract. Using direct numerical magneto-hydrodynamic (MHD) simulations, we demonstrate the evidence of two physically different types of vortex motions in the solar photosphere. Baroclinic motions of plasma in non-magnetic granules are the primary source of vorticity in granular regions of the solar photosphere, however, there is a significantly more efficient mechanism of vorticity production in strongly magnetised intergranular lanes. These swirly motions of plasma in intergranular magnetic field concentrations could be responsible for the generation of different types of MHD wave modes, for example, kink, sausage and torsional Alfvén waves. These waves could transport a relevant amount of energy from the lower solar atmosphere and contribute to coronal plasma heating.

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20

Dritschel, D. G., P. H. Diamond, and S. M. Tobias. "Circulation conservation and vortex breakup in magnetohydrodynamics at low magnetic Prandtl number." Journal of Fluid Mechanics 857 (October 15, 2018): 38–60. http://dx.doi.org/10.1017/jfm.2018.719.

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In this paper we examine the role of weak magnetic fields in breaking Kelvin’s circulation theorem and in vortex breakup in two-dimensional magnetohydrodynamics for the physically important case of a fluid with low magnetic Prandtl number (low $Pm$ ). We consider three canonical inviscid solutions for the purely hydrodynamical problem, namely a Gaussian vortex, a circular vortex patch and an elliptical vortex patch. We examine how magnetic fields lead to an initial loss of circulation $\unicode[STIX]{x1D6E4}$ and attempt to derive scaling laws for the loss of circulation as a function of field strength and diffusion as measured by two non-dimensional parameters. We show that for all cases the loss of circulation depends on the integrated effects of the Lorentz force, with the patch cases leading to significantly greater circulation loss. For the case of the elliptical vortex, the loss of circulation depends on the total area swept out by the rotating vortex, and so this leads to more efficient circulation loss than for a circular vortex.

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21

Acosta, Jesús González, Miryam R. Joya, and J. Barba-Ortega. "Influence of short-range artificial defects in a macroscopic flat disk on the Abrikosov state." International Journal of Modern Physics B 28, no. 32 (December 14, 2014): 1450227. http://dx.doi.org/10.1142/s0217979214502270.

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We study the vortex configuration in a superconducting macroscopic flat disk with central defects in the presence of a uniform applied magnetic field. Owing to the defects nature on the thin disk, vortices are able to form geometry induced, quasi-symmetric configurations of disk, triangle and concentric shells in the rest of the disk. The theoretical study made on this mesoscopic systems allows us to trace not only how the vortex pattern evolves with magnetic field, but also how the defect can be used to show the pinning and anti-pinning effect. The magnetic induction, vortex number, magnetization and Cooper pairs density as a function of the external magnetic field are calculated, we show that in our sample novels vortex configurations are possible due to the size of the disk and if the hole or barrier defect is considered.

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Kirillov, A. A., and E. P. Savelova. "Magnetic traversable wormhole as accelerator of charged particles." International Journal of Modern Physics A 35, no. 02n03 (January 30, 2020): 2040026. http://dx.doi.org/10.1142/s0217751x20400266.

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We show that the scattering of radiation on a traversable wormhole forms a vortex in the radiation energy flux. Then, if the wormhole possesses also a magnetic fields, the vortex accelerates charged particles along the magnetic lines and such a system works as an accelerator. If the vortex is small, the system reaches the stationary state, when the income of the kinetic energy reradiates completely in the form of the synchrotron radiation. Such a mechanism allows us to relate a part of observed sources of the synchrotron radiation to magnetic wormholes.

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23

ELISTRATOV, A. A., O. A. BOBRIKOV, I. L. MAKSIMOV, and V. JEUDY. "GEOMETRICAL BARRIER IN A SUPERCONDUCTING STRIP: SINGLE-VORTEX APPROACH." Modern Physics Letters B 18, no. 01 (January 10, 2004): 19–26. http://dx.doi.org/10.1142/s0217984904006408.

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The problem of the geometrical barrier is solved for the vortex fragment entering from the corners of a superconducting strip, placed into a perpendicular magnetic field. A single-vortex Gibbs potential is constructed for the first time taking into account the actual current/field distribution in a sample of rectangular cross-section. The dependence of the vortex inclination angle as well as the vortex altitude on the external magnetic field is determined. Geometrical barrier-suppression field is found at which near-the-edge vortices start penetrating deep into the strip.

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24

SILVA, E., R. MARCON, R. FASTAMPA, M. GIURA, and S. SARTI. "MAGNETIC FIELD ORIENTATION DEPENDENCE OF THE MICROWAVE RESPONSE IN YBa2Cu3O7-δ." International Journal of Modern Physics B 17, no. 04n06 (March 10, 2003): 929–35. http://dx.doi.org/10.1142/s0217979203016844.

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We present microwave resistivity measurements at 21 GHz in YBa 2 Cu 3 O 7-δ thin film as a function of the temperature and the magnetic field. Measurements are taken in various relative orientations of the microwave current, dc magnetic field and c axis. Attention is focussed on measurements taken with the dc field parallel to the (a, b) planes. In moderate magnetic field, we show that the microwave magnetic response is made up of a vortex motion contribution, which can be described by conventional models, and a noticeable magnetic field induced increase of the quasiparticle density, which exhibits features typical of the existence of lines of nodes in the superconducting gap. We estimate the effective vortex viscosity for vortex motion across the (a, b) planes.

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Vogt, Tobias, Ilmārs Grants, Sven Eckert, and Gunter Gerbeth. "Spin-up of a magnetically driven tornado-like vortex." Journal of Fluid Mechanics 736 (November 14, 2013): 641–62. http://dx.doi.org/10.1017/jfm.2013.552.

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AbstractThe spin-up of a concentrated vortex in a liquid metal cylinder with a free surface is considered experimentally and numerically. The vortex is driven by two flow-independent magnetic body forces. A continuously applied rotating magnetic field provides the source of the angular momentum. A pulse of about one order of magnitude stronger travelling magnetic field drives a converging flow that temporarily focuses this angular momentum towards the axis of the container. A highly concentrated vortex forms that produces a funnel-shaped surface depression. We explore experimentally the duration, the depth and the conditions of formation of this funnel. Additionally, we measure the axial velocity and calculate the axisymmetric flow field of this transient vortex at a lower force magnitude. The spin-up vortex is similar to the corresponding developed time-averaged turbulent vortex driven by the same magnetic forces (Grants et al., J. Fluid Mech., vol. 616, 2008, pp. 135–152). There are two main differences. First, the maximum swirl concentration condition cannot be expressed as a constant ratio of the two driving forces. Second, a much higher degree of swirl concentration is feasible. We explain these differences as due to a much lower turbulence during the spin-up.

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Guo, Zhen Gang, Li Qing Pan, Hong Mei Qiu, M. Yasir Rafique, and Shuai Zeng. "Micromagnetic Simulation of CoFe Magnetic Nanorings: Switching Behavior in External Magnetic Field." Advanced Materials Research 710 (June 2013): 80–84. http://dx.doi.org/10.4028/www.scientific.net/amr.710.80.

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The magnetization reversal processes of magnetic nanorings (Co50Fe50) with different geometric shapes are investigated. In addition to the expected onion and vortex magnetization states, other metastable states are observed in the magnetization processes. We anatomize the formation and transition of magnetic states, and the propagation and annihilation of domain walls in the reversal process through the dynamic picture. Phase diagrams for the magnetization switching behavior depending on the geometric parameters are presented. The simulation shows that the vortex state is stabilized in thick and narrow rings. The switching field from vortex to onion states turns out to increase with thickness and decrease with width and diameter.

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VOVK, R. V., A. V. SAMOILOV, I. L. GOULATIS, and A. CHRONEOS. "INFLUENCE OF INTRINSIC PINNING ON THE RESISTIVE PROPERTIES OF YBa2Cu3O7-δ SINGLE CRYSTALS." Modern Physics Letters B 27, no. 30 (November 21, 2013): 1350220. http://dx.doi.org/10.1142/s0217984913502205.

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The dynamics of vortex matter in YBa 2 Cu 3 O 7-δ single crystal with unidirectional twin boundaries is studied experimentally in a wide range of velocities of the magnetic flux in a tilted magnetic field. It is determined that with the orientation of the magnetic field vector in the locality of the ab-plane, the dynamics of the magnetic flux near the melting temperature of the vortex lattice can be described by the Kim–Anderson model and as the temperature is lowered, by the theory of collective pinning on small-scale defects or by the vortex glass model. The intrinsic pinning caused by the layered crystal structure of the material has an impact on the dynamics of magnetic flux and this effect increases with the decreasing of the temperature.

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28

Carneiro, Gilson. "Interaction between a superconducting vortex and a magnetic vortex." Physica C: Superconductivity 460-462 (September 2007): 1186–87. http://dx.doi.org/10.1016/j.physc.2007.03.422.

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29

Mitin, D., D. Nissen, P. Schädlich, S. S. P. K. Arekapudi, and M. Albrecht. "Single vortex core recording in a magnetic vortex lattice." Journal of Applied Physics 115, no. 6 (February 14, 2014): 063906. http://dx.doi.org/10.1063/1.4865746.

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COSTA, B. V., J. C. S. ROCHA, P. Z. COURA, S. A. LEONEL, D. TOSCANO, and R. A. DIAS. "MAGNETIC VORTEX BEHAVIOR IN NANO-STRUCTURES." International Journal of Modern Physics C 23, no. 08 (August 2012): 1240003. http://dx.doi.org/10.1142/s0129183112400037.

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The existence of a vortex in the ground state of magnetic nano-disks has open a wide range of possibilities for constructing new ultra-compact devices. In this work we study the dynamical behavior of a vortex in a magnetic nano-particle. First, we introduce magnetic impurities in the system. It is observed that depending on the strength of the interaction the impurities can behave both as a pinning (attractive) or scattering (repulsive). By using the known values of the parameters for Permalloy-79 we have calculated the interaction energy of the vortex core with a single defect. We estimated the interaction range as approximately 10 nm. Both results agree quite well with experimental measurements. As a second point we discuss how the vortex dynamics in nano-disks can be used for building a nano-spin valve.

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Boust, Fabrice, and Nicolas Vukadinovic. "Magnetic excitations in assemblies of dipolar coupled nanoparticles." EPJ Web of Conferences 244 (2020): 01015. http://dx.doi.org/10.1051/epjconf/202024401015.

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The equilibrium magnetization configurations and the associated microwave susceptibility spectra of dipolar coupled nanoplatelets are explored using three-dimensional (3D) micromagnetic simulations. First, the case of periodic arrangements of nanoplatelets on square arrays is considered. As a result, a macro-vortex state defined as a flux closure pattern spreading over the whole array with or without a vortex core can be stabilized starting from an initial orthoradial magnetization configuration. For macro-vortex states with a vortex core, the linear excitation spectrum exhibits a sub-GHz resonance line ascribed to the vortex core dynamics at the array center. The features of this line (spectral position and amplitude) depend on the array size and the strength of the dipolar coupling through the interplatelet spacing. This resonance is also observed for macro-vortex states without a vortex core but only in the regime of a strong dipolar coupling. The effect of disorder is then investigated by numerically generating assemblies of nanoplatelets with a position disorder and, shape and size distributions. The micromagnetic simulations reveal flux closure magnetization configurations as well but without a vortex core. A low-frequency resonance appears in the susceptibility spectra for quite high surface contents of nanoplatelets but its amplitude is weaker compared to the case of periodic arrays. This line arises from a collective mode extended over a few nanoplatelets. A large variety of static and dynamical behaviors is thus evidenced resulting in a great complexity even in such model systems.

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32

Liu, Jixing, and Wendell Horton. "The intrinsic electromagnetic solitary vortices in magnetized plasma." Journal of Plasma Physics 36, no. 1 (August 1986): 1–24. http://dx.doi.org/10.1017/s0022377800011557.

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Several Rossby-type vortex solutions constructed for electromagnetic perturbations in magnetized plasma encounter the difficulty that the perturbed magnetic field and the parallel current are not continuous on the boundary between two regions. We find that fourth-order differential equations must be solved to remove this discontinuity. Special solutions for two types of boundary value problem for the fourth-order partial differential equations are presented. By applying these solutions to different nonlinear equations in magnetized plasma, the intrinsic electromagnetic solitary drift-Alfvén vortex (along with solitary Alfvén vortex) and the intrinsic electromagnetic solitary electron vortex (along with short-wavelength drift vortex) are constructed. While still keeping a localized dipole structure, these new vortices have more complicated radial structures in the inner and outer regions than the usual Rossby-wave vortex. The new type of vortex guarantees the continuity of the perturbed magnetic field δB⊥ and the parallel current j‖ on the boundary between inner and outer regions of the vortex. The allowed regions of propagation speeds for these vortices are analysed, and we find that the complementary relation between the vortex propagating speeds and the corresponding phase velocities of the linear modes no longer exists.

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33

Sommeria, Joël. "Electrically driven vortices in a strong magnetic field." Journal of Fluid Mechanics 189 (April 1988): 553–69. http://dx.doi.org/10.1017/s0022112088001144.

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A steady isolated vortex is produced in a horizontal layer of mercury (of thickness a), subjected to a uniform vertical magnetic field. The vortex is forced by an electric current going from an electrode in the lower plane to the circular outer frame. The flow is investigated by streak photographs of small particles following the free upper surface, and by electric potential measurements. The agreement with the asymptotic theory for high values of the Hartmann number M is excellent for moderate electric currents. In particular all the current stays in the thin Hartmann layer of thickness a/M, except in the vortex core of horizontal extension a/M½. For higher currents, the size of the core becomes larger and depends only on the local interaction parameters. When the current is switched off, we measure the decay due to the Hartmann friction. A similar study is carried out for a vortex created by an initial electric pulse, and for a pair of vortices of opposite sign. For all these examples, the dynamics can be described by the two-dimensional Navier-Stokes equations with Hartmann friction, except in the vortex cores. Finally a vortex is produced near a lateral wall and a detachment of the boundary layer parallel to the magnetic field occurs, by which a second vortex of opposite sign is generated.

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34

Singha, Sintu, K. P. Sinhamahapatra, and S. K. Mukherjea. "Control of Vortex Shedding From a Bluff Body Using Imposed Magnetic Field." Journal of Fluids Engineering 129, no. 5 (October 24, 2006): 517–23. http://dx.doi.org/10.1115/1.2717616.

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The two-dimensional incompressible laminar viscous flow of a conducting fluid past a square cylinder placed centrally in a channel subjected to an imposed transverse magnetic field has been simulated to study the effect of a magnetic field on vortex shedding from a bluff body at different Reynolds numbers varying from 50 to 250. The present staggered grid finite difference simulation shows that for a steady flow the separated zone behind the cylinder is reduced as the magnetic field strength is increased. For flows in the periodic vortex shedding and unsteady wake regime an imposed transverse magnetic field is found to have a considerable effect on the flow characteristics with marginal increase in Strouhal number and a marked drop in the unsteady lift amplitude indicating a reduction in the strength of the shed vortices. It has further been observed, that it is possible to completely eliminate the periodic vortex shedding at the higher Reynolds numbers and to establish a steady flow if a sufficiently strong magnetic field is imposed. The necessary strength of the magnetic field, however, depends on the flow Reynolds number and increases with the increase in Reynolds number. This paper describes the algorithm in detail and presents important results that show the effect of the magnetic field on the separated wake and on the periodic vortex shedding process.

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35

Орлов, В. А., А. А. Иванов, and И. Н. Орлова. "Движение взаимодействующих магнитных вихрей в параллельных нанолентах." Физика твердого тела 61, no. 3 (2019): 493. http://dx.doi.org/10.21883/ftt.2019.03.47241.285.

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AbstractThe periodic motion of the interacting vortex domain walls in a pair of nanostripes has been theoretically investigated. As a model, two parallel nanostripes with magnetization inhomogeneities in the form of magnetic vortices have been examined. The magnetic subsystems of the stripes are magnetostatically coupled. The quasi-elastic coupling between vortices ensures the existence of normal modes of the periodic magnetization motion. The frequencies of these modes have been calculated. It is shown that not any combination of the vortex topological charge leads to the resonant behavior of magnetization in ac fields. The effect of the static component of a magnetic field on the frequency of the periodic motion of vortex domain walls is discussed.

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36

Chen, Rui-Pin, and Khian-Hooi Chew. "Far-field properties of a vortex Airy beam." Laser and Particle Beams 31, no. 1 (November 27, 2012): 9–15. http://dx.doi.org/10.1017/s0263034612000729.

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AbstractAnalytical far-field expressions for the transverse electric mode and transverse electric magnetic mode terms, and the energy flux distributions of vortex Airy beams are derived based on the vector angular spectrum of the beam and the stationary phase method. The physical pictures of vortex Airy beams from the vectorial structure are illustrated and the energy flux distributions are demonstrated in far-field. The influences of the beam parameters, especially the exponential factor, on the energy flux distributions of vortex Airy beams and its transverse electric mode and transverse electric magnetic mode terms are discussed. This work provides a new understanding of the propagation behaviors and applications of a vortex Airy beam.

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37

BAJER, KONRAD, and H. K. MOFFATT. "On the effect of a central vortex on a stretched magnetic flux tube." Journal of Fluid Mechanics 339 (May 25, 1997): 121–42. http://dx.doi.org/10.1017/s0022112097005466.

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Experiments and numerical simulations of fully developed turbulence reveal the existence of elongated vortices whose length is of the order of the integral scale of turbulence while the diameter is somewhere between the Kolmogorov scale and the Taylor microscale. These vortices are embedded in quasi-irrotational background flow whose straining action counteracts viscous decay and determines their cross-sectional shape. In the present paper we analyse the effect of a stretched vortex of this kind on a uni-directional magnetic flux tube aligned with vorticity in an electrically conducting fluid. When the magnetic Prandtl number is large, Pm[gsim ]1, the field is concentrated in a flux tube which, like the vortex itself, has elliptical cross-section inclined at 45° to the principal axes of strain. We focus on the limit Pm[Lt ]1 when the magnetic flux tube has radial extent much larger than that of the vortex, which appears like a point vortex as regards its action on the flux tube. We find the steady-state solution valid in the entire plane outside the vortex core. The solution shows that the magnetic field has a logarithmic spiral component and no definite orientation of the inner contours. Such magnetized vortices may be expected to exist in MHD turbulence with weak magnetic field where the field shows a tendency to align itself with vorticity. Magnetized vortices may also be expected to exist on the solar surface near the corners of convection cells where downwelling swirling flow tends to concentrate the magnetic field.

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38

SITENKO, YU A., and N. D. VLASII. "THE AHARONOV-BOHM EFFECT IN SCATTERING OF QUASICLASSICAL PARTICLES." International Journal of Modern Physics: Conference Series 14 (January 2012): 551–60. http://dx.doi.org/10.1142/s2010194512007684.

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Quantum-mechanical scattering of nonrelativistic charged particles by a magnetic vortex of nonzero transverse size is considered. The high-frequency limit of a scattered particle corresponds to the quasiclassical limit, and we show that the scattering Aharonov-Bohm effect persists in the quasiclassical limit owing to the Fraunhofer diffraction in the forward direction. Therefore, the flux of a magnetic vortex serves as a gate for the propagation of quasiclassical particles moving orthogonally to the vortex. The issue of the experimental detection of the Fraunhofer diffraction peak and the scattering Aharonov-Bohm effect is discussed.

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39

Browne, P. F. "Phenomena Involving Magnetic Vortex Tubes." Symposium - International Astronomical Union 140 (1990): 136–38. http://dx.doi.org/10.1017/s0074180900189776.

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Magnetic vortex tubes (MVTs) on a hierarchy of scales occur universally. On the largest scale they channel bipolar outflows of gas. A pinched region of MVT provides an acceleration mechanism capable of yielding the maximum cosmic ray energies.

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40

Zharkov, G. F., and V. G. Zharkov. "Magnetic Vortex in Superconducting Wire." Physica Scripta 57, no. 6 (June 1, 1998): 664–67. http://dx.doi.org/10.1088/0031-8949/57/6/011.

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41

Yuan, H. Y., and X. R. Wang. "Nano magnetic vortex wall guide." AIP Advances 5, no. 11 (November 2015): 117104. http://dx.doi.org/10.1063/1.4935276.

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42

Subramani, A., D. Geerpuram, A. Domanowski, V. Baskaran, and V. Metlushko. "Vortex state in magnetic rings." Physica C: Superconductivity 404, no. 1-4 (May 2004): 241–45. http://dx.doi.org/10.1016/j.physc.2003.11.044.

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43

Browne, P. F. "Magnetic Vortex Tubes in Astrophysics." IEEE Transactions on Plasma Science 14, no. 6 (December 1986): 718–39. http://dx.doi.org/10.1109/tps.1986.4316622.

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44

Fried, Jasper P., and Peter J. Metaxas. "Nanoparticle-Modified Magnetic Vortex Dynamics." IEEE Magnetics Letters 8 (2017): 1–5. http://dx.doi.org/10.1109/lmag.2017.2684744.

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45

Kammerer, Matthias, Markus Sproll, Hermann Stoll, Matthias Noske, Markus Weigand, Christian Illg, Manfred Fähnle, and Gisela Schütz. "Delayed magnetic vortex core reversal." Applied Physics Letters 102, no. 1 (January 7, 2013): 012404. http://dx.doi.org/10.1063/1.4773592.

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46

Roy, Pinaki. "Magnetic point vortex and parasupersymmetry." Physics Letters B 305, no. 4 (May 1993): 353–56. http://dx.doi.org/10.1016/0370-2693(93)91067-w.

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47

Tziotziou, K., G. Tsiropoula, and I. Kontogiannis. "A persistent quiet-Sun small-scale tornado." Astronomy & Astrophysics 623 (March 2019): A160. http://dx.doi.org/10.1051/0004-6361/201834679.

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Context. Recently, the appearance, characteristics, and dynamics of a persistent 1.7 h vortex flow, resembling a small-scale tornado, have been investigated with observations both from the ground and from space in a quiet-Sun region in several lines and channels and for the first time in the Hα line centre. The vortex flow showed significant substructure in the form of several intermittent chromospheric swirls. Aims. We investigate the oscillatory behaviour of various physical parameters in the vortex area in an attempt to better understand the physics of the reported vortex flow. This is the first analysis of this extent. Methods. We used the same data set of high spatial and temporal resolution CRisp Imaging SpectroPolarimeter (CRISP) observations in several wavelengths along the Hα and Ca II 8542 Å line profiles, as well as Doppler velocities and full-width at half-maximum (FWHM) derived from the Hα line profiles. The spectral analysis of oscillations is based on a two-dimensional wavelet analysis performed within the vortex flow area and in a quiet-Sun region (used for comparison), as well as along line and circular slices. Results. The vortex flow shows significant oscillatory power in the range of 3–5 min, peaking around 4 min. This power behaves differently than the reference quiet-Sun region. The derived oscillations reflect the cumulative action of different components such as swaying motions, rotation, and waves. The derived periods for swaying motions are in the range of 200–220 s, and the rotation periods are ∼270 s for Hα and ∼215 s for Ca II 8542 Å. Periods increase with atmospheric height and seem to decrease with radial distance from the vortex centre, suggesting a deviation from a rigid rotation. The behaviour of power within the vortex flow as a function of period and height implies the existence of evanescent waves. Moreover, considerable power is obtained even for periods as long as 10 min, not only at photospheric but also at chromospheric heights, while the formation of vortexes is related to turbulent convection or to twisting motions exercised in the magnetic field concentrations. These imply that different types of waves may be excited, such as magnetoacoustic (e.g. kink) or Alfvén waves. Conclusions. The vortex flow seems to be dominated by two motions: a transverse (swaying) motion, and a rotational motion. The obtained oscillations point to the propagation of waves within it. Nearby fibril-like flows could play an important role in the rotational modulation of the vortex flow. There also exists indirect evidence that the structure is magnetically supported, and one of the swirls, close to its centre, seems to be acting as a “central engine” to the vortex flow.

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48

Krynytskyi, Yuri, and Andrij Rovenchak. "Multipole expansions for time-dependent charge and current distributions in quasistatic approximation." Modern Physics Letters A 34, no. 02 (January 20, 2019): 1950018. http://dx.doi.org/10.1142/s0217732319500184.

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We propose a consistent approach to the definition of electric, magnetic and toroidal multipole moments. Electric and magnetic fields are split into potential, vortex and radiative terms, with the latter ones dropped off in the quasistatic approximation. The potential part of the electric field, the vortex parts of the magnetic field and vector potential contain gradients of scalar functions. Formally introducing magnetic and toroidal analogs of the electric charge, we apply multipole expansions for those scalars. Closed-form expressions are derived in an arbitrary order for electric, magnetic and toroidal multipoles, which constitute a full system for expansions of the electromagnetic field.

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49

Karpov, P. I., and S. I. Mukhin. "Polarizability of electrically induced magnetic vortex “atoms”." EPJ Web of Conferences 185 (2018): 07003. http://dx.doi.org/10.1051/epjconf/201818507003.

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Electric field control of magnetic structures, particularly topological defects in magnetoelectric materials, draws a great attention, which has led to experimental success in creation and manipulation of single magnetic defects, such as skyrmions and domain walls. In this work we explore a scenario of electric field creation of another type of topological defects – magnetic vortices and antivortices. Because of interaction of magnetic and electric subsystems each magnetic vortex (antivortex) in magnetoelectric materials possesses quantized magnetic charge, responsible for interaction between vortices, and electric charge that couples them to electric field. This property of magnetic vortices makes possible their creation by electric fields. We show that the electric field, created by a cantilever tip, produces a “magnetic atom” with a localized spot of ordered vortices (“nucleus” of the atom) surrounded by antivortices (“electronic shells”). We analytically find the vortex density distribution profile and temperature dependence of polarizability of this structure and confirm it numerically by Monte Carlo simulation.

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50

Requerey, Iker S., Basilio Ruiz Cobo, Milan Gošić, and Luis R. Bellot Rubio. "Persistent magnetic vortex flow at a supergranular vertex." Astronomy & Astrophysics 610 (February 2018): A84. http://dx.doi.org/10.1051/0004-6361/201731842.

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Context. Photospheric vortex flows are thought to play a key role in the evolution of magnetic fields. Recent studies show that these swirling motions are ubiquitous in the solar surface convection and occur in a wide range of temporal and spatial scales. Their interplay with magnetic fields is poorly characterized, however. Aims. We study the relation between a persistent photospheric vortex flow and the evolution of a network magnetic element at a supergranular vertex. Methods. We used long-duration sequences of continuum intensity images acquired with Hinode and the local correlation-tracking method to derive the horizontal photospheric flows. Supergranular cells are detected as large-scale divergence structures in the flow maps. At their vertices, and cospatial with network magnetic elements, the velocity flows converge on a central point. Results. One of these converging flows is observed as a vortex during the whole 24 h time series. It consists of three consecutive vortices that appear nearly at the same location. At their core, a network magnetic element is also detected. Its evolution is strongly correlated to that of the vortices. The magnetic feature is concentrated and evacuated when it is caught by the vortices and is weakened and fragmented after the whirls disappear. Conclusions. This evolutionary behavior supports the picture presented previously, where a small flux tube becomes stable when it is surrounded by a vortex flow.

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