1,966 results on '"vortex state"'
Search Results
202. Scanning tunneling spectroscopy studies on vortices in YBa2Cu3Oy single crystals
- Author
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Shibata, Kenji, Maki, Makoto, Nishizaki, Terukazu, and Kobayashi, Norio
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BARIUM compounds , *SCANNING tunneling microscopy , *MAGNETIC fields , *CRYSTAL etching - Abstract
Low-temperature scanning tunneling spectroscopy (STS) has been performed on YBa2Cu3Oy (YBCO) in the magnetic field
μ0H=1 T. Clear vortex images are obtained on the surface chemically etched with 1% Br-ethanol. We measured on the twinned crystals and directly observed the effect of twin boundary on the vortex arrangement. Vortices close to the twin boundary align themselves parallel to it, suggesting that vortices are effectively trapped by the twin boundary. The vortices very close to the twin boundary form almost square lattice. Such tendency decreases with increasing distance and the vortices form a hexagonal lattice in the region far from the twin boundary. However, the orientation of hexagonal lattice is not consistent with the previous reports. Possible origins of such disagreement are described in this paper. We also show spectra observed in the scan region and discuss their features. [Copyright &y& Elsevier]- Published
- 2003
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203. Plausiblity of Antiferromagnetism in and near RBCO Vortex Cores:: An ME-μSR Analysis.
- Author
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Boekem, C., Tien, A. Y., Hughes, L., Ruiz, E. J., and Cavanaugh, S. X.
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ANTIFERROMAGNETISM , *SUPERCONDUCTIVITY , *THERMODYNAMICS , *ENTROPY - Abstract
Maximum-Entropy (ME) analysis is applied to muon-spin-rotation (μSR) data of RBa[sub 2]Cu[sub 3]O[sub y] (RBCO; R = Ho, Eu) vortex states. Our focus is on the prospect of antiferromagnetism (AF) associated with the vortex core. The ME transforms are fitted by two μSR signals: the vortex signal and the grain-boundary (GB) signal. Below T[sub c], the GB signals are well fitted by Gaussians for both EuBCO (T[sub c] = 94 K) and underdoped HoBCO (T[sub c] = 66 K). Below 0.5T[sub c], EuBCO and HoBCO vortex signals are best fitted using Lorentzians, instead of expected Gaussians. An estimate for an effective Neél temperature of an AF vortex core is about 30 K. Our AF-core search results for RBCO vortex states are discussed considering a magnetic origin of cuprate superconductivity. [ABSTRACT FROM AUTHOR]
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- 2003
204. Thermal conductivity in vortex state of nodal superconductors
- Author
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Won, H. and Maki, K.
- Subjects
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SUPERCONDUCTORS , *MAGNETIC fields - Abstract
How to determine the symmetry of the superconducting order parameter is one of the important issues in novel superconductors, which include charge conjugated organic superconductors. We have proposed that the angular dependence of the thermal conductivity in a planar magnetic field provides a new window to look at the symmetry of the order parameter. After a brief summary of the quasiclassical approach we describe how the symmetry of the superconducting order parameter in Sr
2 RuO4 , CeCoIn5 andκ -(ET)2 Cu(NCS)2 is determined. Also in some of experiments the phononic thermal conductivity plays the crucial role. [Copyright &y& Elsevier]- Published
- 2003
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205. Josephson vortices in <f>Bi2Sr2CaCu2O8+δ</f> single crystal
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Hirata, Kazuto, Ooi, Shuuichi, and Mochiku, Takashi
- Subjects
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SUPERCONDUCTORS , *JOSEPHSON effect - Abstract
Josephson vortices in Bi
2 Sr2 CaCu2 O8+δ single crystals have been studied to measure the vortex-flow resistance with the current perpendicular to the superconducting layers, sweeping the parallel magnetic fields. In the flow resistance, we have found novel periodic oscillations. The period of the oscillations corresponds to adding “one” flux quantum per “two” intrinsic Josephson junctions. It is considered that the oscillations take place with a coherent motion of the vortices in the dynamical flow. These results suggest that the Josephson vortices form a triangular lattice in the ground state, related to the matching effect between the sample width and the lattice spacing along the layers. It is also suggested that they will be applicable to a new type of magnetic sensor. [Copyright &y& Elsevier]- Published
- 2002
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206. Different roles of anisotropy and disorder on the vortex matter of Bi2Sr2CaCu2O<f>8+δ</f> single crystal.
- Author
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Darminto, D., Diantoro, M., Sutjahja, I.M., Nugroho, A.A., Loeksmanto, W., and Tjia, M.O.
- Subjects
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MAGNETIZATION , *ANISOTROPY - Abstract
The oxygen doped and Pb-substituted single crystalline Bi2Sr2CaCu2O
8+δ samples havingTc,on and anisotropy(γ2) ranging respectively from 65 to 93 K and from 773 to 49,715 have been studied in the basis of magneto-resistance and magnetization data. It is found that the lowering of anisotropy due to higher oxygen content or Pb substitution is responsible for the reduction of magnetic field-induced transitional broadening and a shift ofHirr(T) andHg(T) to higher temperatures and magnetic field. Meanwhile, the increasing disorder manifested by decreasingTc also leads to the extended range of appearance for the second magnetization peak (SMP) and enlarged critical glassy region. It is shown that decreasing anisotropy does not necessarily lead to the lowering ofTc in contrast to the monotonic dependence ofTc on the disorder measured in the temperature range of SMP effect. Additionally, a remarkable monotonic correlation betweenTc and the glassy exponent s has been established. [Copyright &y& Elsevier]- Published
- 2002
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207. Josephson vortex flow in Bi2Sr2CaCu2O<f>8+δ</f>: Periodic oscillations of flow resistance.
- Author
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Hirata, Kazuto, Ooi, Shuuichi, and Mochiku, Takashi
- Subjects
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BISMUTH , *MAGNETIC fields - Abstract
We have measured the Josephson vortex flow resistance with the current perpendicular to the Cu–O layers of Bi2Sr2CaCu2O
8+δ . It has been found that novel periodic oscillations appear in the flow resistance with sweeping the magnetic field parallel to the layers. The oscillations have been observed in a wide range of parallel fields larger than 6 kOe and only in a smaller current density than about 100 A/cm2. The period of the oscillations corresponds to adding “one” flux quantum per “two” intrinsic Josephson junctions. These results suggest that the Josephson vortices form a triangular lattice as a ground state. [Copyright &y& Elsevier]- Published
- 2002
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208. Effect of an impulsive force on vortices in a rotating Bose–Einstein condensate
- Author
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Adhikari, Sadhan K. and Muruganandam, Paulsamy
- Subjects
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BOSE-Einstein condensation , *VORTEX motion , *SUPERFLUIDITY - Abstract
The effects of a sudden increase and decrease of the interatomic interaction and harmonic-oscillator trapping potential on vortices in a quasi two-dimensional rotating Bose–Einstein condensate are investigated using the mean-field Gross–Pitaevskii equation. We also study the decay of vortices when the rotation of the condensate is suddenly stopped. Upon a free expansion of a rotating BEC with vortices the radius of the vortex core increases more rapidly than the radius of the condensate. [Copyright &y& Elsevier]
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- 2002
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209. A new phenomenon of Josephson vortex flow in Bi2Sr2CaCu2O<f>2+δ</f>
- Author
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Hirata, Kazuto, Ooi, Shuuichi, and Mochiku, Takashi
- Subjects
- *
JOSEPHSON junctions , *SUPERCONDUCTORS , *OSCILLATIONS , *MAGNETIC fields - Abstract
In the vortex-flow resistance measured with the current perpendicular to the superconducting layers of Bi
2 Sr2 CaCu2 O8+δ , we have found novel periodic oscillations with sweeping the magnetic field parallel to the layers. The oscillations have been observed in a wide range of parallel fields larger than 6 kOe and only in a smaller current region than 200μ A. The period of the oscillations corresponds to adding “one” flux quantum per “two” intrinsic Josephson junctions. These results suggest that the Josephson vortices form a triangular lattice in moving vortices, related to the matching between the sample width and the lattice spacing along the layers, and supply important evidence for new applications. [Copyright &y& Elsevier]- Published
- 2002
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210. Magnetic imaging and dissipation force microscopy of vortices on superconducting Nb films
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Roseman, M. and Grütter, P.
- Subjects
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NIOBIUM , *MAGNETIC force microscopy , *SUPERCONDUCTORS - Abstract
Constant height imaging using a custom built low temperature magnetic force microscope has been performed on patterned and unpatterned superconducting Nb films. Tip induced motion of the vortices is shown, as a function of both tip–sample separation and temperature. Constant height dissipation images of vortices suggest eddy current damping as well as vortex motion within potential wells as major sources of energy loss. [Copyright &y& Elsevier]
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- 2002
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211. Modulation in the non-uniformity of the vortex state across the peak effect: evidence via the magnetic quadrupole moment in a very clean crystal of 2H–NbSe<f>2</f> for <f>H∥c</f>
- Author
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Pal, D., Ramakrishnan, S., Grover, A.K., Higgins, M.J., and Chandran, Mahesh
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SUPERCONDUCTORS , *QUADRUPOLE moments - Abstract
The non-uniform magnetic character of the mixed (vortex) state is known to result in a magnetic quadrupolar response of a type-II superconductor. The nucleation of stronger pinned regions coexisting with weaker pinned regions across the peak effect (PE) in a weakly pinned superconductor has been demonstrated using ac scanning Hall bar microscopy by Marchevsky et al. [Nature 409 (2001) 591]. Coexistence of this nature could produce an imprint in the measured quadrupolar response of such samples. We present successful detection of such an imprint across the PE region of a very clean crystal of 2H–NbSe
2 forH∥c via a well-established procedure of preferentially recording a signal arising from the non-uniformity in the magnetization of the sample in a vibrating sample magnetometer. [Copyright &y& Elsevier]- Published
- 2002
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212. Entanglement propagation of a quantum optical vortex state
- Author
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Abir Bandyopadhyay, Dhruba Banerjee, Ravindra Pratap Singh, and Anindya Banerji
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Photon ,FOS: Physical sciences ,Physics::Optics ,Quantum entanglement ,Squashed entanglement ,01 natural sciences ,law.invention ,010309 optics ,Spontaneous parametric down-conversion ,law ,Quantum mechanics ,0103 physical sciences ,Wigner distribution function ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,010306 general physics ,Physics ,Quantum Physics ,Atomic and Molecular Physics, and Optics ,Vortex state ,Electronic, Optical and Magnetic Materials ,Quantum electrodynamics ,Quantum Physics (quant-ph) ,Optical vortex ,Beam splitter ,Optics (physics.optics) ,Physics - Optics - Abstract
We study the entanglement evolution of a quantum optical vortex state propagating through coupled lossless waveguides. We consider states generated by coupling two squeezed modes using a sequence of beam splitters and also by subtracting photons from the signal in spontaneous parametric down conversion. We reconstruct the Wigner function at a later time to study the correlation and quantify the entanglement after propagation using \emph{logarithmic negativity}., 8 pages, 6 figures, RevTeX 4. Minor corrections in this version
- Published
- 2016
213. Novel π -type vortex in a nanoscale extreme type-II superconductor: Induced by quantum-size effect
- Author
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Wenhui Zhang, Haiyan Huang, Qing Liu, and Yajiang Chen
- Subjects
Superconductivity ,Physics ,Local density of states ,Condensed matter physics ,Condensed Matter - Superconductivity ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Critical value ,01 natural sciences ,Vortex state ,Electronic, Optical and Magnetic Materials ,Coherence length ,Vortex ,Superfluidity ,Condensed Matter::Superconductivity ,0103 physical sciences ,Electrical and Electronic Engineering ,010306 general physics ,0210 nano-technology ,Type-II superconductor - Abstract
By numerically solving the Bogoliubov-de Gennes equations, we report a novel $\pi$-type vortex state whose order parameter near the core undergoes an extraordinary $\pi$-phase change for a quantum-confined extreme type-II $s$-wave superconductor. Its supercurrent behaves as the cube of the radial coordinate near the core, and its local density of states spectrum exhibits a significant negative-shifted zero-bias peak. Such $\pi$-type vortex state is induced by quantum-size effect, and can survive thermal smearing at temperatures up to a critical value $T_\tau$. The Anderson's approximation indicates that the $\pi$-type vortex may remain stable under sufficiently week magnetic field in the case less deep in the type-II limit. Moreover, we find that its appearance is governed by the sample size and $k_F\xi_0$ with $k_F$ the Fermi wave number and $\xi_0$ the zero-temperature coherence length. Similar effects may be expected in quantum-confined ultracold superfluid Fermi gasses, or even high-$T_c$ superconductors with proper $k_F\xi_0$ value., Comment: 6 figures
- Published
- 2016
214. Magnetic vortex state applied in magnetoresistive sensors (Conference Presentation)
- Author
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Herbert Weitensfelder, Wolfgang Raberg, Armin Satz, Klemens Pruegl, Dieter Suess, Hubert Brückl, Sebastian Luber, and Juergen Zimmer
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Physics ,Condensed Matter::Materials Science ,Magnetization ,Tunnel magnetoresistance ,Hysteresis ,Ferromagnetism ,Condensed matter physics ,Magnetoresistance ,Giant magnetoresistance ,Vortex state ,Vortex - Abstract
Magnetoresistive sensors based on giant magnetoresistance (GMR) or tunnel magnetoresistance (TMR) play a major role towards the miniaturization in the industrial society. Typically, spin-valve-type magnetoresistive sensors are embedded in a Wheatstone bridge configuration with rectangular, meander-like or elliptically shaped thin film elements. Such elements usually switch via multi-domain, C- or S-shaped magnetization states and, therefore, often exhibit an open non-linear hysteresis curve. Linearity and hysteretic effects are key features in the improvement of such sensors. We will present a different approach by using circularly shaped elements exhibiting a different magnetization state of a magnetic vortex [1]. This is one of the fundamental magnetization ground states occurring in disk-shaped thin film elements and is characterized by minimization of the demagnetizing energy at the expense of exchange energy. Experimental data were generated on electrically contacted GMR and TMR disks which were fabricated by optical lithography. The following advantages will be discussed and compared to standard elliptical sensor elements. (a) The vortex state shows essentially no hysteresis in the minor loop. (b) Since the vortex nucleation happens prior to the zero field, the M(H=0)=0 crossing is independent of history. (c) The critical fields can be easily controlled by the element geometry. (d) The noise is low. All characteristic experimental values have been determined in dependence of free layer thickness, disk diameter and temperature. These findings are discussed in the frame of the semi-analytical rigid-vortex-model [2] and micromagnetic simulations. The financial support by the Austrian Federal Ministry of Science, Research and Economy and the Christian Doppler Research Association in Austria is gratefully acknowledged. [1] D. Suess, A. Bachleitner-Hofmann, A. Satz, H. Weitensfelder, C. Vogler, F. Bruckner, C. Abert, K. Prugl, J. Zimmer, C. Huber, S. Luber, W. Raberg, T. Schrefl, H. Bruckl, „Topologically Protected Vortex Structures to Realize Low-Noise Magnetic Sensors with High Linear Range”, Nature Electronics 1, 362 (2018) [2] K. Y. Guslienko et al., “Magnetization reversal due to vortex nucleation, displacement, and annihilation in submicron ferromagnetic dot arrays”, Phys. Rev. B 65 (2001)
- Published
- 2019
215. Bistability of magnetic states in Fe-Pd nanocap arrays
- Author
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M. Marszałek, Manfred Albrecht, Mary Ap, Senoy Thomas, Michael Heigl, Joachim Gräfe, C R Rajgowrav, M.R. Anantharaman, P B Aravind, Michal Krupinski, Felix Groß, and Mario Fix
- Subjects
Materials science ,Bistability ,Condensed matter physics ,Mechanical Engineering ,Nucleation ,Bioengineering ,02 engineering and technology ,General Chemistry ,Atmospheric temperature range ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Vortex state ,0104 chemical sciences ,Vortex ,Magnetic field ,Mechanics of Materials ,General Materials Science ,Electrical and Electronic Engineering ,Magnetic alloy ,Single domain ,0210 nano-technology - Abstract
Magnetic bistability between vortex and single domain states in nanostructures are of great interest from both fundamental and technological perspectives. In soft magnetic nanostructures, the transition from a uniform collinear magnetic state to a vortex state (or vice versa) induced by a magnetic field involves an energy barrier. If the thermal energy is large enough for overcoming this energy barrier, magnetic bistability with a hysteresis-free switching occurs between the two magnetic states. In this work, we tune this energy barrier by tailoring the composition of FePd alloys, which were deposited onto self-assembled particle arrays forming magnetic vortex structures on top of the particles. The bifurcation temperature, where a hysteresis-free transition occurs, was extracted from the temperature dependence of the annihilation and nucleation field which increases almost linearly with Fe content of the magnetic alloy. This study provides insights into the magnetization reversal process associated with magnetic bistability, which allows adjusting the bifurcation temperature range by the material properties of the nanosystem.
- Published
- 2019
216. Crossover of polar and toroidal orders in ferroelectric nanodots with a morphotropic phase boundary and nonvolatile polar-vortex transformations
- Author
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Yue Zheng, Wenfang Chen, and Ye Ji
- Subjects
Phase boundary ,Materials science ,Condensed matter physics ,02 engineering and technology ,Dielectric ,021001 nanoscience & nanotechnology ,01 natural sciences ,Ferroelectricity ,Vortex state ,Vortex ,Condensed Matter::Materials Science ,Polar vortex ,0103 physical sciences ,Polar ,Nanodot ,010306 general physics ,0210 nano-technology - Abstract
Ferroelectric vortices are promising candidates for developing high-capacity memory devices and discovery of intriguing electromechanical properties. It is well known that the ferroelectric vortex state tends to stabilize at poor screening conditions and a relatively good screening condition would give rise to a polar state. However, what happens at the intermediate screening condition remains unclear. In this work, by including a Bardeen screening model into phase-field simulations, we explore the screening-mediated state stabilization in ferroelectric nanodots. A state coexistence regime where the polar and toroidal orders can both stabilize in a ferroelectric nanodot is found at certain range of screening (that is, screening length from 0.011 to 0.022 nm at room temperature). The mechanism of state coexistence is analyzed by construction of the input-dependent free-energy profile according to the energy minimum principle. The coexistence regime is further revealed to be tunable by geometrical parameters. Importantly, the polar and vortex states can be readily switched between each other via electrical and mechanical loads, paving the way towards a type of nonvolatile multilevel memory. Moreover, a screening-mediated morphotropic phase boundary (MPB) with strong dielectric and piezoelectric responses is demonstrated. Our study thus discovers a stability crossover of polar and toroidal orders in ferroelectric nanodots at intermediate screening condition accompanied with superior electromechanical properties and the feasibility in multilevel memory application.
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- 2019
217. Influence of an applied current on the vortex matter in a superconducting sample with structural defects
- Author
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A.S. de Arruda, C. A. Aguirre, Q. D. Martins, and José José Barba-Ortega
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0301 basic medicine ,Superconductivity ,Physics ,Multidisciplinary ,Condensed matter physics ,Electron ,Vorticity ,Magnetic susceptibility ,Vortex state ,Article ,Vortex ,Magnetic field ,03 medical and health sciences ,Magnetization ,030104 developmental biology ,0302 clinical medicine ,Electromagnetism ,Condensed Matter::Superconductivity ,lcsh:H1-99 ,lcsh:Social sciences (General) ,lcsh:Science (General) ,030217 neurology & neurosurgery ,lcsh:Q1-390 - Abstract
We show how the inclusion of a structural defect of determined geometry controls the vortex state in a square superconducting sample in the presence of an external magnetic field and a dc current. We simulated the defects by using the deformation parameter τ ( x , y ) , solving the non-lineal time-dependent Ginzburg-Landau equations and using the link variable method, for four different geometries as possible options for the storage vortex, simulating the behavior of a capacitor. We found an exponential dependence of the current in which the first vortex penetrates the sample J → c as a function of the area of a square central defect in the sample. We also show the effect of the defects and the transport current on the magnetization, magnetic susceptibility, vorticity, and magnetic field at the first vortex entry into the sample H 1 and the density of the superconducting electrons.
- Published
- 2019
218. Subcritical turbulent condensate in rapidly rotating Rayleigh-Bénard convection
- Author
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Edgar Knobloch, Benjamin Favier, Céline Guervilly, Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and Lawrence Berkeley National Laboratory [Berkeley] (LBNL)
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Convection ,Physics ,Bistability ,Turbulence ,Mechanical Engineering ,Mechanics ,Physics - Fluid Dynamics ,Condensed Matter Physics ,01 natural sciences ,Vortex state ,010305 fluids & plasmas ,Vortex ,Physics::Fluid Dynamics ,symbols.namesake ,Mechanics of Materials ,Cascade ,0103 physical sciences ,symbols ,[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] ,Rayleigh scattering ,010306 general physics ,Physics::Atmospheric and Oceanic Physics ,Geostrophic wind - Abstract
The possibility of subcritical behaviour in the geostrophic turbulence regime of rapidly rotating thermally driven convection is explored. In this regime a non-local inverse energy transfer may compete with the more traditional and local direct cascade. We show that, even for control parameters for which no inverse cascade has previously been observed, a subcritical transition towards a large-scale vortex state can occur when the system is initialized with a vortex dipole of finite amplitude. This new example of bistability in a turbulent flow, which may not be specific to rotating convection, opens up new avenues for studying energy transfer in strongly anisotropic three-dimensional flows., Comment: 12 pages, 6 figures
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- 2019
219. Morphology and Functional Properties of Magnetic Nanoparticles of Lanthanum-Strontium Manganites
- Author
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I.V. Fesych, D.V. Chernov, Li Quan-Jun, Vladimir Pitsyuga, N.A. Liedienov, A.V. Voznyak, Igor Zatovskyi, A. V. Pashchenko, Georgiy Levchenko, Ziyu Wei, and Eduard E. Zubov
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Diffraction ,Phase transition ,Strontium ,Materials science ,Analytical chemistry ,Nanoparticle ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Vortex state ,chemistry ,0103 physical sciences ,Magnetic refrigeration ,Lanthanum ,Magnetic nanoparticles ,010306 general physics ,0210 nano-technology - Abstract
Structure, morphology, magnetic state and magnetocaloric effect of single-phase nanopowder La 0.6 Sr 0.4 MnO 3 manganites have been investigated by X-ray diffraction, BET, SEM, and magnetic methods. According to X-ray diffraction, BET and SEM data, an average size of particles for the La 0.6 Sr 0.4 MnO 3 composition is tens of nanometers. On the basis of analysis of the magnetic data, the magnetic states, phase transition temperatures, magnetocaloric effect as well as critical sizes of particles, i.e. boundary sizes of a single-domain state, a vortex state and a multi-domain state, have been determined. The most part of nanoparticles of the La 0.6 Sr 0.4 MnO 3 composition are in the single-domain state.
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- 2019
220. Theory of Magnetic Domain Phases in Ferromagnetic Superconductors
- Author
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Zh. Devizorova, S. Mironov, Alexandre I. Buzdin, Kotelnikov Institute of Radio Engineering and Electronics (IRE), Russian Academy of Sciences [Moscow] (RAS), Centre de physique moléculaire optique et hertzienne (CPMOH), Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1, Laboratoire Ondes et Matière d'Aquitaine (LOMA), and Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Superconductivity ,Physics ,[PHYS]Physics [physics] ,Magnetic structure ,Condensed matter physics ,Magnetic domain ,Magnetism ,Transition temperature ,Condensed Matter - Superconductivity ,FOS: Physical sciences ,General Physics and Astronomy ,01 natural sciences ,Vortex state ,Superconductivity (cond-mat.supr-con) ,[PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con] ,Ferromagnetism ,Condensed Matter::Superconductivity ,0103 physical sciences ,Curie temperature ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,010306 general physics - Abstract
Recently discovered superconducting P-doped EuFe$_2$As$_2$ compounds reveal the situation when the superconducting critical temperature substantially exceeds the ferromagnetic transition temperature. The main mechanism of the interplay between magnetism and superconductivity occurs to be an electromagnetic one and a short period magnetic domain structure was observed just below Curie temperature [Stolyarov et al., Sci. Adv. \textbf{4}, eaat1061 (2018)]. We elaborate a theory of such transition and demonstrate how the initial sinusoidal magnetic structure gradually transforms into a soliton-like domain one. Further cooling may trigger a first-order transition from the short-period domain Meissner phase to the self-induced ferromagnetic vortex state and we calculate the parameters of this transition. The size of the domains in the vortex state is basically the same as in the normal ferromagnet, but with the domain walls which should generate the set of vortices perpendicular to the vortices in the domains., 6 pages, 4 figures
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- 2019
221. Chiral vortices and pseudoscalar condensation due to rotation
- Author
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Pengfei Zhuang, Yin Jiang, Lingxiao Wang, and Lianyi He
- Subjects
Nuclear Theory ,High Energy Physics::Lattice ,FOS: Physical sciences ,01 natural sciences ,Topological defect ,Nuclear Theory (nucl-th) ,Superconductivity (cond-mat.supr-con) ,Superfluidity ,High Energy Physics - Phenomenology (hep-ph) ,Quantum mechanics ,Condensed Matter::Superconductivity ,0103 physical sciences ,010306 general physics ,Physics ,Condensed Matter::Quantum Gases ,010308 nuclear & particles physics ,Condensed Matter - Superconductivity ,Condensation ,Vortex state ,Vortex ,Pseudoscalar ,High Energy Physics - Phenomenology ,Quantum Gases (cond-mat.quant-gas) ,Chiral symmetry breaking ,Ground state ,Condensed Matter - Quantum Gases - Abstract
We investigate the influence of rotation on the dynamical chiral symmetry breaking in strongly interacting matter. We develop a self-consistent Bogoliubov-de Gennes-like theoretical framework to study the inhomogeneous chiral condensate and the possible chiral vortex state in rotating finite-size matter in four-fermion interacting theories. We show that for sufficiently rapid rotation in $2+1$ dimensions, the ground state can be a chiral vortex state, a type of topological defect in analogy to superfluids and superconductors. The vortex state exhibits pion condensation, providing a new mechanism to realize pseudoscalar condensation in strongly interacting matter., 8 pages, 3 figures, resubmitted to PRD as a regular article
- Published
- 2019
222. Distribution characteristics on droplet deposition of wind field vortex formed by multi-rotor UAV
- Author
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Shuang Guo, Jiyu Li, Yeyin Shi, Li Yifan, Zhan Yilong, and Weixiang Yao
- Subjects
0106 biological sciences ,Atmospheric Science ,Aircraft ,Evaporation ,Droplet deposition ,Wind ,Physical Chemistry ,01 natural sciences ,Multidisciplinary ,Vaporization ,Flight Testing ,Physics ,Eukaryota ,Agriculture ,04 agricultural and veterinary sciences ,Mechanics ,Conical surface ,Plants ,Condensed Matter Physics ,Crop Production ,Chemistry ,Experimental Organism Systems ,Rotors ,Physical Sciences ,Engineering and Technology ,Medicine ,Agrochemicals ,Phase Transitions ,Research Article ,Materials science ,Science ,Airflow ,Aerospace Engineering ,Crops ,Research and Analysis Methods ,Meteorology ,Plant and Algal Models ,Grasses ,Pesticides ,Fertilizers ,Aerosols ,Surface Treatments ,Mechanical Engineering ,Organisms ,Wind field ,Biology and Life Sciences ,Humidity ,Penetration (firestop) ,Models, Theoretical ,Vortex state ,Chemical Deposition ,Vortex ,Downwash ,Manufacturing Processes ,Animal Studies ,Earth Sciences ,040103 agronomy & agriculture ,0401 agriculture, forestry, and fisheries ,Rice ,Pest Control ,Crop Science ,010606 plant biology & botany - Abstract
When the unmanned aerial vehicle (UAV) is used for aerial spraying, the downwash airflow generated by the UAV rotor will interact with the crop canopy and form a conical vortex shape in the crop plant. The size of the vortex will directly affect the outcome of the spraying operation. Six one-way spraying were performed by the UAV in a rice field with different but random flying altitude and velocities within the optimal operational range to form different vortex patterns. The spraying reagent was clear water, which was collected by water sensitive paper (WSP), and then the WSP was analyzed to study the droplets deposition effects in different vortex states. The results showed that the formation of the vortex significantly influenced the droplet deposition. To be specific, the droplet deposition amount in the obvious-vortex (OV) state was about 1.5 times of that in the small-scale (SV) vortex state, and 7 times of that in the non-vortex (NV) state. In the OV state, the droplets mainly deposited directly below and on both sides of the route. The deposition amount, coverage rate and droplet size increased from top to bottom of the crops with the deposition amount, coverage rate, and volume median diameter (VMD) ranging 0.204-0.470 μL/cm2, 3.31%-7.41%, and 306-367μm, respectively. In the SV state, droplets mainly deposited in the vortex area directly below the route. The deposition amount in the downwind direction was bigger than that in the upwind direction. The maximum of deposition amount, coverage rate and droplet size were found in the middle layer of the crops, the range are 0.177-0.334μL/cm2, 2.71%-5.30%, 295-370μm, respectively. In the NV state, the droplet mainly performed drifting motion, and the average droplet deposition amount in the downwind non-effective region was 29.4 times of that in the upwind non-effective region and 8.7 times of the effective vortex region directly below the route. The maximum of deposition amount, coverage rate and droplet size appeared in the upper layer of the crop, the range are 0.006-0.132μL/cm2, 0.17%-1.82%, 120-309μm, respectively, and almost no droplet deposited in the middle and lower part of the crop. The coefficient of variation (CV) of the droplet deposition amount was less than 40% in the state of obvious-vortex and small-scale vortex, and the worst penetration appeared in the non-vortex amounting to 65.97%. This work offers a basis for improving the spraying performance of UAV.
- Published
- 2019
223. Numerical Simulation of Abrikosov Vortex at Columnar Defect in Superconductor
- Author
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V.A. Fedirko, A. L. Kasatkin, Sergey Polyakov, and M.V. Fedirko
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010302 applied physics ,Superconductivity ,Abrikosov vortex ,Work (thermodynamics) ,Materials science ,Condensed matter physics ,Computer simulation ,Physics ,QC1-999 ,02 engineering and technology ,Vorticity ,021001 nanoscience & nanotechnology ,01 natural sciences ,Vortex state ,Vortex ,Condensed Matter::Superconductivity ,0103 physical sciences ,0210 nano-technology ,Displacement (fluid) - Abstract
We report a numerical modeling of single vortex depinning and its subsequent dynamics in HTS film with extended linear defects under the influence of the transport current. Numerical simulation of stable pinned vortex state and its escape from a linear defect has been performed. The non-stationary dynamics of vortex escape has been investigated and time-dependent solution for vortex displacement from the defect has been obtained. The delay effect in vortex escape process has been studied and the time delay has been estimated. The impact of processes being studied on electrodynamic properties of a superconductor has also been discussed. The dynamics of vortex escape from columnar pinning site described in the present work is important both for understanding of vortex dynamics and applying high-Tc superconductors with columnar defects.
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- 2019
224. Exploring the impact of core expansion on the vortex distribution in superconducting–normal-metal hybrid nanostructures
- Author
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Victor Moshchalkov, Cun Xue, Matias Timmermans, Joris Van de Vondel, Bart Raes, Ritika Panghotra, National Natural Science Foundation of China, Methuselah Foundation, Flemish Government, Natural Science Foundation of Shaanxi Province, Research Foundation - Flanders, and European Commission
- Subjects
Technology ,Materials science ,Characteristic length ,Scanning tunneling spectroscopy ,Materials Science ,DIRTY ,Materials Science, Multidisciplinary ,02 engineering and technology ,01 natural sciences ,Physics, Applied ,Condensed Matter::Superconductivity ,0103 physical sciences ,010306 general physics ,VORTICES ,Superconductivity ,Mesoscopic physics ,Science & Technology ,Condensed matter physics ,Bilayer ,Physics ,021001 nanoscience & nanotechnology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Vortex state ,Vortex ,Magnetic field ,Physics, Condensed Matter ,STATES ,DENSITY ,Physical Sciences ,0210 nano-technology - Abstract
The superconducting condensate in a bilayer normal-metal–superconducting film has a nonuniform dependence throughout the layer. For sufficiently thin normal metallic films, the superconducting correlations induced by the contacting superconducting layer result in the formation of a minigap and the characteristic length scales governing the response of the condensate will be different. In this work we use scanning tunneling spectroscopy to visualize the vortex states as a function of the applied magnetic field in a Au-MoGe nanostructure. By comparing the obtained zero-bias conductance maps with time-dependent Ginzburg-Landau simulations, we directly confirm that the observed vortex distributions can only be explained by taking into account the impact of the normal metallic layer. We illustrate this impact on the vortex state for two lithographically fabricated mesoscopic bilayer structures containing an identical antidot array but having different lateral sizes., R.P., B.R, V.V.M., and J.V.d.V. acknowledge support from the Methusalem funding by the Flemish government and the Flemish Science Foundation (Grant No. G0B5315N). C.X. acknowledges support by the National Natural Science Foundation of China (Grant No. 11702218) and the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2018JM1003). This work has been supported by the COST action NanoCoHybri (Grant No. CA16218).
- Published
- 2019
225. Noise-induced transition from superfluid to vortex state in two-dimensional nonequilibrium polariton condensates
- Author
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Vladimir N. Gladilin and Michiel Wouters
- Subjects
Physics ,Quantum fluid ,Condensed Matter::Quantum Gases ,Field (physics) ,Condensed matter physics ,Condensed Matter::Other ,FOS: Physical sciences ,Non-equilibrium thermodynamics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Vortex state ,Superfluidity ,Quantum Gases (cond-mat.quant-gas) ,Condensed Matter::Superconductivity ,0103 physical sciences ,Polariton ,Condensed Matter::Statistical Mechanics ,Relaxation (physics) ,Condensed Matter - Quantum Gases ,010306 general physics ,0210 nano-technology ,Noise (radio) - Abstract
We study the Berezinskii-Kosterlitz-Thouless mechanism for vortex-antivortex pair formation in two-dimensional superfluids for nonequilibrium condensates. Our numerical study is based on a classical field model for driven-dissipative quantum fluids that is applicable to polariton condensates. We investigate the critical noise needed to create vortex-antivortex pairs in the systems, starting from a state with uniform phase. The dependence of the critical noise on the nonequilibrium and energy relaxation parameters is analyzed in detail.
- Published
- 2019
226. Nonlinear dynamics of Josephson vortices in merging superfluid rings
- Author
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Boris A. Malomed, Alexander Yakimenko, and Artem Oliinyk
- Subjects
Population ,FOS: Physical sciences ,Pattern Formation and Solitons (nlin.PS) ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Superfluidity ,law ,Condensed Matter::Superconductivity ,0103 physical sciences ,010306 general physics ,education ,Physics ,Condensed Matter::Quantum Gases ,Numerical Analysis ,education.field_of_study ,Condensed matter physics ,Applied Mathematics ,Persistent current ,Nonlinear Sciences - Pattern Formation and Solitons ,Vortex state ,Vortex ,Gross–Pitaevskii equation ,Quantum Gases (cond-mat.quant-gas) ,Modeling and Simulation ,Dissipative system ,Condensed Matter - Quantum Gases ,Bose–Einstein condensate - Abstract
We consider merger of two parallel toroidal atomic Bose-Einstein condensates with different vorticities in a three-dimensional (3D) trap. In the tunnel-coupling regime, Josephson vortices (rotational fluxons) emerge in the barrier between the superflows. When the barrier is gradually eliminated, we observe essentially three-dimensional evolution of quantum vortices, which may include the development of the Kelvin-Helmholtz instability at the interface between the rings, in the framework of a weakly dissipative Gross-Pitaevskii equation. An initially more populated ring, carrying a persistent current, can drag an initially non-rotating less populated one into the same vortex state. The final state of the condensate crucially depends on an initial population imbalance in the double-ring set, as well as on the shape of the 3D trapping potential, oblate or prolate. In the prolate (axially elongated) configuration, robust 3D hybrid structures may appear as a result of the merger of persistent currents corresponding to different vorticities., Comment: 11 pages, 8 figures, to be published in Commun. Nonlin. Sci. Num. Sim
- Published
- 2019
- Full Text
- View/download PDF
227. Chiral and helical p -wave superconductivity in doped bilayer BiH
- Author
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Lin Yang, Wan-Sheng Wang, Qiang-Hua Wang, and Da Wang
- Subjects
Physics ,Superconductivity ,Strongly Correlated Electrons (cond-mat.str-el) ,Spins ,Condensed matter physics ,Condensed Matter - Superconductivity ,Van Hove singularity ,FOS: Physical sciences ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Coupling (probability) ,01 natural sciences ,Vortex state ,Superconductivity (cond-mat.supr-con) ,Condensed Matter - Strongly Correlated Electrons ,Condensed Matter::Superconductivity ,Pairing ,0103 physical sciences ,Spin density wave ,010306 general physics ,0210 nano-technology ,Spin-½ - Abstract
We investigate the superconductivity (SC) driven by correlation effects in electron-doped bilayer BiH near a type-II van Hove singularity (vHS). By functional renormalization group, we find triplet $p$-wave pairing prevails in the interaction parameter space, except for spin density wave (SDW) closer to the vHS or when the interaction is too strong. Because of the large atomic spin-orbital coupling (SOC), the $p$-wave pairing occurs between equal-spin electrons, and is chiral and two-fold degenerate. The chiral state supports in-gap edge states, even though the low energy bands in the SC state are topologically trivial. The absence of mirror symmetry allows Rashba SOC that couples unequal spins, but we find its effect is of very high order, and can only drive the chiral $p$-wave into helical $p$-wave deep in the SC state. Interestingly, there is a six-fold degeneracy in the helical states, reflected by the relative phase angle $\theta=n\pi/3$ (for integer $n$) between the spin components of the helical pairing function. The phase angle is shown to be stable in the vortex state., Comment: 6 page, 6 figures, supplemental materials included in source files
- Published
- 2018
228. Direct observation of spin diffusion enhanced nonadiabatic spin torque effects in rare-earth-doped permalloy
- Author
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Andrii V. Chumak, A. Conca, Julia Osten, Mathias Kläui, Jürgen Fassbender, Pascal Krautscheid, Jonathan Ehrler, Daniel Schönke, Isabella Boventer, Robert M. Reeve, and Burkard Hillebrands
- Subjects
Permalloy ,Physics ,Angular momentum ,Condensed matter physics ,Rare earth ,Doping ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Polarization (waves) ,01 natural sciences ,Vortex state ,0103 physical sciences ,Spin diffusion ,010306 general physics ,0210 nano-technology ,Scaling - Abstract
The relation between the nonadiabaticity parameter $\ensuremath{\beta}$ and the damping parameter $\ensuremath{\alpha}$ is investigated in permalloy-based microdisks. In order to determine $\ensuremath{\beta}$, high-resolution imaging of the current-induced vortex-core displacement is performed using scanning electron microscopy with polarization analysis. The materials properties of the films are varied via rare-earth Dy doping, leading to a greatly enhanced damping, while retaining the same spin configuration for the confined vortex state. A clear trend to much higher nonadiabaticity values is seen for the higher doping levels and an averaged value of $\ensuremath{\beta}=(0.29\ifmmode\pm\else\textpm\fi{}0.15)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$ is determined for $1.73%$ Dy doping, compared to $(0.067\ifmmode\pm\else\textpm\fi{}0.014)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$ which is extracted for pure permalloy. This is supportive of a similar scaling of $\ensuremath{\beta}$ and $\ensuremath{\alpha}$ in this system, pointing to a common origin of the spin relaxation which is at the heart of nonadiabatic transport and the dissipation of angular momentum that provides damping, in line with theoretical calculations.
- Published
- 2018
229. Noise Characterization of Vortex-State GMR Sensors with Different Free Layer Thicknesses
- Author
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Dieter Suess, Armin Satz, Herbert Weitensfelder, and Hubert Brueckl
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noise ,Materials science ,Condensed matter physics ,Magnetoresistance ,Spin valve ,GMR ,Giant magnetoresistance ,lcsh:A ,Pink noise ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Vortex state ,Vortex ,Magnetization ,vortex state ,giant magnetoresistance ,lcsh:General Works ,Noise (radio) - Abstract
The spin valve principle is the most prominent sensor design among giant- (GMR) and tunneling (TMR) magnetoresistive sensors. A new sensor concept with a disk shaped free layer enables the formation of a flux-closed vortex magnetization state if a certain relation of thickness to diameter is given. The low frequency noise of current-in-plane GMR sensing elements with different free layer thicknesses at different external field strengths has been measured. The measurements of the 1/f noise in external fields enabled a separation of magnetic and electric noise contributions. It has been shown that while the sensitivity is increasing with a decreasing element thickness, the pink noise contribution is increasing too. Still the detection limit at low frequencies is better in thinner free layer elements due to the higher sensitivity.
- Published
- 2018
230. Comparison of Sensitivity and Low-Frequency Noise Contributions in Giant-Magnetoresistive and Tunneling-Magnetoresistive Spin-Valve Sensors with a Vortex-State Free Layer
- Author
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Juergen Zimmer, Dieter Suess, Herbert Weitensfelder, Sebastian Luber, Roman Windl, Wolfgang Raberg, Armin Satz, Klemens Pruegl, Florian Bruckner, Claas Abert, Hubert Brueckl, and Anton Bachleitner-Hofmann
- Subjects
010302 applied physics ,Physics ,Magnetoresistance ,Condensed matter physics ,Spin valve ,General Physics and Astronomy ,Biasing ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Noise (electronics) ,Vortex state ,Magnetic field ,Magnetization ,0103 physical sciences ,Sensitivity (control systems) ,0210 nano-technology - Abstract
For giant- (GMR) and tunneling- (TMR) magnetoresistive sensors, noise and sensitivity are crucial in determining the smallest magnetic field that can be detected. Both parameters are analyzed for a sensor design comprising a circular free layer that features a flux-closed vortex magnetization state. The authors find that in the low-frequency regime, where noise is predominantly pink, the detectivity depends $o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}y$ on the active sensor area, not on the magnetoresistance ratio or bias voltage, and is the same for both GMR and TMR devices. As such sensors are widely used in $e.g.$ biomedical, automotive, and aerospace applications, this insight is expected to be far-reaching.
- Published
- 2018
231. Barkhausen Imaging: A magneto-optical approach to mapping the pinning landscape in soft ferromagnetic films
- Author
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Jeremy Trimble and Jesse Berezovsky
- Subjects
010302 applied physics ,Permalloy ,Kerr effect ,Materials science ,Condensed matter physics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Vortex state ,Displacement (vector) ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Vortex ,Magnetization ,Magneto-optic Kerr effect ,Condensed Matter::Superconductivity ,0103 physical sciences ,0210 nano-technology - Abstract
We demonstrate a magneto-optical microscopy technique to create two-dimensional images of the pinning behavior of a vortex state as it is translated through a soft ferromagnetic film. The resulting information yields a map of how defects and inhomogeneities in the material serve to trap high-energy-density magnetization configurations such as vortex cores or domain walls. We raster scan a vortex core within a thin permalloy disk using in-plane magnetic fields, and monitor the vortex displacement using the magneto-optical Kerr effect. The differential nature of the measurement yields spatial resolution ≈ 5 nm, much less than the diffraction limit, and minimum resolvable pinning energy ≈ 0.4 eV. The technique produces two images, one displaying the pinning-induced vortex displacement relative to the expected free motion, and the other displaying hysteretic vortex displacement between the trace and re-trace. We demonstrate the technique on two samples, extract quantitative statistics about the pinning landscape, and compare to simulated results with a pinning landscape derived from the measured surface topography of the samples.
- Published
- 2021
232. Goal-driven method for decoding the configuration of coherent wave groups required for the generation of arbitrary-order vortex lattices
- Author
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Huakun Zhang, Zhigang Liu, Kunpeng Liu, and Xiaochun Dong
- Subjects
Physics ,Field (physics) ,business.industry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Interference (wave propagation) ,Topology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Vortex state ,Vortex ,010309 optics ,Amplitude ,Optics ,Lattice (order) ,Harmonics ,0103 physical sciences ,0210 nano-technology ,business ,Optical vortex - Abstract
Together, the number of waves, wave vectors, amplitudes, and additional phases constitute the coherent wave group configuration and determine the pattern of the interference field. Identifying an appropriate wave group configuration is key to generating vortex lattices via interferometry. Previous studies have approached this task by first assigning the four elements, then calibrating the vortex state of the interference field. However, this method has failed to progress beyond generating third-order vortex lattices, which are insufficient for some practical applications. Therefore, this study proposes a method for determining the proper wave group configurations corresponding to arbitrary-order vortex lattices. We adopt a goal-driven approach: First, we set a vortex lattice as the target field and model it, before decomposing the target field into a sum of multiple harmonics using Fourier transforms. These harmonics constitute the wave group required to generate the target vortex lattice. As vortex lattices of any order can be set as the target field, the proposed method is compatible with any mode order. Simulations and experiments were conducted for fourth- and fifth-order vortex lattices, thus demonstrating the effectiveness of the proposed method.
- Published
- 2021
233. Spin–torque dynamics for noise reduction in vortex-based sensors
- Author
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Claude Fermon, Ursula Ebels, Shinji Yuasa, Vincent Cros, Kay Yakushiji, Myriam Pannetier-Lecoeur, Akio Fukushima, Steffen Wittrock, Aurélie Solignac, Paolo Bortolotti, J. Moulin, Sumito Tsunegi, Hitoshi Kubota, Mafalda Jotta Garcia, and Romain Lebrun
- Subjects
010302 applied physics ,Physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Magnetoresistance ,Noise reduction ,FOS: Physical sciences ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Noise (electronics) ,Vortex state ,Vortex ,Magnetization ,Condensed Matter::Superconductivity ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,0210 nano-technology ,Order of magnitude ,Spin-½ - Abstract
The performance of magnetoresistive sensors is today mainly limited by their 1/f low-frequency noise. Here, we study this noise component in vortex-based TMR sensors. We compare the noise level in different magnetization configurations of the device, i.e., vortex state or uniform parallel or antiparallel states. We find that the vortex state is at least an order of magnitude noisier than the uniform states. Nevertheless, by activating the spin-transfer-induced dynamics of the vortex configuration, we observe a reduction of the 1/f noise, close to the values measured in the AP state, as the vortex core has a lower probability of pinning into defect sites. Additionally, by driving the dynamics of the vortex core by a non-resonant rf field or current, we demonstrate that the 1/f noise can be further decreased. The ability to reduce the 1/f low-frequency noise in vortex-based devices by leveraging their spin-transfer dynamics thus enhances their applicability in the magnetic sensors' landscape.
- Published
- 2021
234. Vortices in a superconducting two-band disk: Role of the Josephson and bi-quadratic coupling
- Author
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C. A. Aguirre, Q. D. Martins, and José José Barba-Ortega
- Subjects
010302 applied physics ,Coupling ,Physics ,Superconductivity ,Electron density ,Condensed matter physics ,Energy Engineering and Power Technology ,Condensed Matter Physics ,01 natural sciences ,Vortex state ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Vortex ,Magnetization ,Quadratic equation ,Condensed Matter::Superconductivity ,0103 physical sciences ,Electrical and Electronic Engineering ,010306 general physics - Abstract
This paper shows the effect of the Josephson and bi-quadratic coupling types on the vortex state, the magnetization in a two-band superconducting disk in the presence of an external magnetic field and the effect that the γ value has on the vortex state. This study is based on the two bands Ginzburg-Landau time dependent theory, and the main properties are presented via Ab-Initio of MgB 2 . The superconducting electron density and the magnetic response of the material are also calculated for several temperatures and we present the state of unconventional vortices for each superconductor band. Finally, it is shown that there is a predominant band in this type material for weak coupling, this is also supported by the ab-initio study.
- Published
- 2021
235. Synchronized full vortices as topological spin-Meissner states in spinor exciton–polariton condensates
- Author
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Szu-Cheng Cheng, Shih-Da Jheng, and Ting-Wei Chen
- Subjects
Condensed Matter::Quantum Gases ,Physics ,Zeeman effect ,Spinor ,Statistical and Nonlinear Physics ,Topology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Vortex state ,Vortex ,Magnetic field ,010309 optics ,symbols.namesake ,Condensed Matter::Superconductivity ,0103 physical sciences ,symbols ,Polariton ,Zeeman energy ,Spin-½ - Abstract
The spin-Meissner effect is a phenomenon in which the Zeeman energy splitting of a spinor exciton–polariton condensate in a magnetic field is suppressed. If a topological state shows this effect, the state is called the topological spin-Meissner (TSM) state. We found that a vortex state of a spinor MPC in which each spin component carries a phase singularity in a magnetic field could be a TSM state. The physical properties of a TSM state in full vortices are affected by nonlinear spin-anisotropic interactions among polaritons, spin-flipping rates, and Zeeman energy splitting. Bistable TSM states in full vortices exist, as the magnetic field strength is below a critical strength, which depends on the pump power. The distributions of the degrees of circular polarization of full vortices are also studied.
- Published
- 2021
236. Magnetic textures in hemispherical thin film caps with in-plane exchange bias
- Author
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Andreea Tomita, Dennis Holzinger, Arno Ehresmann, Maximilian Merkel, Rico Huhnstock, and Meike Reginka
- Subjects
010302 applied physics ,Kerr effect ,Materials science ,Condensed matter physics ,Magnetometer ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Vortex state ,law.invention ,Condensed Matter::Materials Science ,Exchange bias ,Ferromagnetism ,law ,0103 physical sciences ,Magnetic force microscope ,Thin film ,0210 nano-technology ,Anisotropy - Abstract
Hemispherical caps of in-plane exchange biased IrMn/CoFe layer systems have been fabricated on top of regularly arranged spherical silica particles by magnetron sputtering, creating magnetic Janus particles. In this thin film layer system cap, the magnetic shape anisotropy of the topographically non-flat hemispheres competes with the unidirectional anisotropy induced by the exchange bias. The magnetic properties of this non-trivial system have been investigated by longitudinal magneto-optical Kerr effect magnetometry, where a characterization method has been developed considering both the curved layer system and the signal contributions of flat parts of the sputtered thin film system. Both remagnetization curves, from Kerr magnetometry and the magnetic force microscopy images, reveal an onion state in the magnetic caps of the ensemble. Additional micromagnetic simulations show a stabilization of the onion state due to the introduced unidirectional anisotropy also in individual hollow hemispheres as compared to the vortex state exhibited by purely ferromagnetic caps.
- Published
- 2021
237. Astigmatic hybrid SU(2) vector vortex beams: towards versatile structures in longitudinally variant polarized optics
- Author
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Xing Fu, Darryl Naidoo, Andrew Forbes, Zhaoyang Wang, and Yijie Shen
- Subjects
Quantum optics ,Physics ,Angular momentum ,business.industry ,Physics::Optics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Polarization (waves) ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Vortex state ,010309 optics ,Optics ,Singularity ,0103 physical sciences ,Coherent states ,Light beam ,0210 nano-technology ,business ,Structured light - Abstract
Structured light with more controllable degrees-of-freedom (DoFs) is an exciting topic with versatile applications. In contrast to conventional vector vortex beams (VVBs) with two DoFs of orbital angular momentum (OAM) and polarization, a hybrid ray-wave structure was recently proposed [Optica 7, 820 (2020)10.1364/OPTICA.382994], which simultaneously manifests multiple DoFs such as ray trajectory, coherent state phase, trajectory combination, besides OAM and polarization. Here we further generalize this exotic structure as the astigmatic hybrid VVB by hatching a new DoF of astigmatic degree. Importantly, the transverse topology varies with propagation, e.g. a linearly distributed hybrid trajectory pattern can topologically evolve to a circularly polygonal star shape, where the number of singularity changes from zero to multiple in a single beam. The propagation-dependent evolution can be easily controlled by the astigmatic degree, including as a vector vortex state such that different astigmatic trajectories have different polarizations. We experimentally generate such beams from a simple laser with a special astigmatic conversion by combined spherical and cylindrical lenses, and the results agree well with our theoretical simulation. With our new structured light, the propagation-multiplexing multi-DoF patterns can be controlled in a single beam, which can largely extend related applications such as high-dimensional large-capacity optical communication, laser machining, and particle trapping.
- Published
- 2020
238. Calorimetric properties of a superconducting anisotropic square: ZFC process
- Author
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Q. D. Martins, José José Barba-Ortega, and C. A. Aguirre
- Subjects
Superconductivity ,Mesoscopic physics ,Materials science ,Condensed matter physics ,Statistical and Nonlinear Physics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Square (algebra) ,Vortex state ,Magnetic field ,Entropy (classical thermodynamics) ,0103 physical sciences ,Cooper pair ,010306 general physics ,0210 nano-technology ,Anisotropy - Abstract
We analyzed the role of the inclusion of anti-dots on the vortex state and some calorimetric properties of a mesoscopic superconducting square immersed in an external applied magnetic field. We calculated the magnetization, entropy, Gibbs free energy, density of Cooper pairs and specific heat for this system in a zero field cooling process, solving the time-dependent Ginzburg–Landau equations. We found that the critical temperature is non-dependent on the number of anti-dots and dependent slightly on the size of the defects. Oscillations in the entropy and specific heat are found due the temperature dependence of the superconducting characteristics length.
- Published
- 2020
239. Irreversible evolution of angular-dependent coercivity in Fe80Ni20 nanowire arrays: Detection of a single vortex state
- Author
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A.H. Montazer, S. Samanifar, M. Alikhani, M. Almasi Kashi, and Abdolali Ramazani
- Subjects
Materials science ,Condensed matter physics ,Nanowire ,02 engineering and technology ,Coercivity ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Aspect ratio (image) ,Vortex state ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Transverse plane ,Magnetization ,Domain wall (magnetism) ,0103 physical sciences ,010306 general physics ,0210 nano-technology - Abstract
The irreversible evolution of magnetic coercivity in arrays of 75 nm diameter Fe 80 Ni 20 nanowires (NWs) has been explored by means of first-order reversal curve (FORC) analysis as a function of the angle between the magnetic field and the NW axis (0°≤ θ ≤90°). The Fe 80 Ni 20 NWs with lengths up to 60 μm were fabricated using a pulsed electrodeposition method into hard-anodic aluminum oxide templates with an interpore distance of 275 nm. Investigating the interwire and intrawire magnetostatic interactions, the angular FORC (AFORC) diagrams indicated enhanced intrawire interactions with increasing length and θ ( θ =83° for 60 μm long NWs. At θ =90°, the NWs reversed magnetization through transverse domain wall, involving a reversible component by a fraction of 95%. Furthermore, the transition angle between the reversal modes was found to decrease with increasing aspect ratio from 200 to 800. The irreversible angular-dependent coercivity ( H c Irrev ( θ )) of Fe 80 Ni 20 NWs was extracted from the AFORC measurements and compared with the major angular dependence of coercivity ( H c Major ( θ )) obtained from the conventional hysteresis loop measurements. While H c Major ( θ ) showed a non-monotonic behavior, H c Irrev ( θ ) constantly increased with increasing θ ( H c Irrev ( θ ) for irreversible switching of VDW when 0°≤ θ ≤86°.
- Published
- 2016
240. Acoustic-Wave-Induced Magnetization Switching of Magnetostrictive Nanomagnets from Single-Domain to Nonvolatile Vortex States
- Author
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Gary M. Atkinson, Dhritiman Bhattacharya, Supriyo Bandyopadhyay, Noel D'Souza, Jayasimha Atulasimha, and Vimal Sampath
- Subjects
Materials science ,Condensed matter physics ,Mechanical Engineering ,Bioengineering ,Magnetostriction ,02 engineering and technology ,General Chemistry ,Acoustic wave ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Nanomagnet ,Vortex state ,Magnetic field ,Vortex ,Condensed Matter::Materials Science ,Magnetization ,0103 physical sciences ,General Materials Science ,Single domain ,010306 general physics ,0210 nano-technology - Abstract
We report experimental manipulation of the magnetic states of elliptical cobalt magnetostrictive nanomagnets (with nominal dimensions of ∼340 nm × 270 nm × 12 nm) delineated on bulk 128° Y-cut lithium niobate with acoustic waves (AWs) launched from interdigitated electrodes. Isolated nanomagnets (no dipole interaction with any other nanomagnet) that are initially magnetized with a magnetic field to a single-domain state with the magnetization aligned along the major axis of the ellipse are driven into a vortex state by acoustic waves that modulate the stress anisotropy of these nanomagnets. The nanomagnets remain in the vortex state until they are reset by a strong magnetic field to the initial single-domain state, making the vortex state nonvolatile. This phenomenon is modeled and explained using a micromagnetic framework and could lead to the development of extremely energy efficient magnetization switching methodologies for low-power computing applications.
- Published
- 2016
241. On the Shape of Meissner Solutions to a Limiting Form of Ginzburg–Landau Systems
- Author
-
Xingfei Xiang
- Subjects
Superconductivity ,Curl (mathematics) ,Condensed matter physics ,Mechanical Engineering ,010102 general mathematics ,Nucleation ,01 natural sciences ,Instability ,Vortex state ,Magnetic field ,010101 applied mathematics ,Mathematics (miscellaneous) ,Condensed Matter::Superconductivity ,0101 mathematics ,Penetration depth ,Tangential and normal components ,Analysis ,Mathematics - Abstract
In this paper we study a semilinear system involving the curl operator, which is a limiting form of the Ginzburg–Landau model for superconductors in \({{\mathbb{R}}^3}\) for a large value of the Ginzburg–Landau parameter. We consider the locations of the maximum points of the magnitude of solutions, which are associated with the nucleation of instability of the Meissner state for superconductors when the applied magnetic field is increased in the transition between the Meissner state and the vortex state. For small penetration depth, we prove that the location is not only determined by the tangential component of the applied magnetic field, but also by the normal curvatures of the boundary in some directions. This improves the result obtained by Bates and Pan in Commun. Math. Phys. 276, 571–610 (2007). We also show that the solutions decay exponentially in the normal direction away from the boundary if the penetration depth is small.
- Published
- 2016
242. Cyclone–anticyclone vortex asymmetry mechanism and linear Ekman friction
- Author
-
S. G. Chefranov
- Subjects
Physics ,Ekman layer ,media_common.quotation_subject ,General Physics and Astronomy ,Radius ,Mechanics ,Rotation ,01 natural sciences ,Instability ,Asymmetry ,Vortex state ,010305 fluids & plasmas ,Vortex ,Physics::Fluid Dynamics ,0103 physical sciences ,Ekman number ,010306 general physics ,Physics::Atmospheric and Oceanic Physics ,media_common - Abstract
Allowance for the linear Ekman friction has been found to ensure a threshold (in rotation frequency) realization of the linear dissipative–centrifugal instability and the related chiral symmetry breaking in the dynamics of Lagrangian particles, which leads to the cyclone–anticyclone vortex asymmetry. An excess of the fluid rotation rate ω0 over some threshold value determined by the fluid eigenfrequency ω (i.e., ω0 > ω) is shown to be a condition for the realization of such an instability. A new generalization of the solution of the Karman problem to determine the steady-state velocity field in a viscous incompressible fluid above a rotating solid disk of large radius, in which the linear Ekman friction was additionally taken into account, has been obtained. A correspondence of this solution and the conditions for the realization of the dissipative–centrifugal instability of a chiral-symmetric vortex state and the corresponding cyclone–anticyclone vortex asymmetry has been shown. A generalization of the well-known spiral velocity distribution in an “Ekman layer” near a solid surface has been established for the case where the fluid rotation frequency far from the disk ω differs from the disk rotation frequency ω0.
- Published
- 2016
243. Magnetic vortex core in cylindrical nanostructures: Looking for its stability in terms of geometric and magnetic parameters
- Author
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A. Riveros, Juan Escrig, Dora Altbir, Eugenio E. Vogel, N. Vidal-Silva, and P. Landeros
- Subjects
Physics ,Nanostructure ,Condensed matter physics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Magnetic phase diagram ,01 natural sciences ,Stability (probability) ,Vortex state ,Electronic, Optical and Magnetic Materials ,Vortex ,Core (optical fiber) ,Ferromagnetism ,Condensed Matter::Superconductivity ,0103 physical sciences ,010306 general physics ,0210 nano-technology ,Phase diagram - Abstract
The relative stability of out-of-plane ferromagnetic, vortex without core and vortex with core configurations in cylindrical nanostructures are examined in terms of their geometric and magnetic parameters. Numerical calculations are done for general geometrical structures, while analytical expressions are obtained in the limiting cases of very long nanostructures. A magnetic phase diagram that clearly identifies the parameters required to obtain a vortex with core as minimum energy configuration is obtained by computing the transition lines between these configurations. The results define the geometric and magnetic parameters for which the vortex state can be made more stable by removing the highly energetic vortex core. Finally, a phase diagram that may be useful for the potencial use of vortices in technological applications is obtained and discussed.
- Published
- 2016
244. Resistive transition and flux flow mechanism in CoFe 2 O 4 nanoparticles added Cu 0.5 Tl 0.5 Ba 2 Ca 2 Cu 3 O 10−δ superconductor
- Author
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S. Qamar, Irfan Qasim, Kashif Nadeem, M. Waqee-ur-Rehman, and Muhammad Waseem Mumtaz
- Subjects
Arrhenius equation ,Superconductivity ,Materials science ,Flux pinning ,Condensed matter physics ,Mechanical Engineering ,Metals and Alloys ,02 engineering and technology ,Activation energy ,021001 nanoscience & nanotechnology ,01 natural sciences ,Vortex state ,symbols.namesake ,Mechanics of Materials ,Electrical resistivity and conductivity ,0103 physical sciences ,Materials Chemistry ,symbols ,Magnetic nanoparticles ,010306 general physics ,0210 nano-technology ,Critical field - Abstract
(CoFe2O4)x/Cu0.5Tl0.5Ba2Ca2Cu3O10−δ {(CoFe2O4)x/CuTl-1223}; (0 ≤ x ≤ 2) nanoparticles-superconductor composites were synthesized by solid–state reaction technique and dissipative mechanism was investigated by infield measurements and analysis. Activation energy {Uo(H)} was calculated from Arrhenius plots of infield resistivity measurements. The infield resistive properties of superconductors depend upon the fluxoid motion, which causes resistive transition broadening by shifting Tc (0) towards lower temperature values. The enhancement of transition broadening is attributed to spread of upper critical field in vortex state and dissipation process with applied magnetic field. Addition of magnetic CoFe2O4 nanoparticles reduces the fluxoid motion by introducing nano-sized defects in the host CuTl-1223 superconducting matrix, which act as effective flux pinning centers. An overall increase in the activation energy Uo(H) has been observed with increasing contents of magnetic CoFe2O4 nanoparticles, which elucidate the enhanced flux pinning with increasing CoFe2O4 magnetic nanoparticles content up to x = 1.5 wt. % in CuTl-1223 superconducting matrix.
- Published
- 2016
245. Deterministic Switching of the Magnetization States in Cobalt Nanorings
- Author
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Manohar Lal, S. Sakshath, and P. S. Anil Kumar
- Subjects
010302 applied physics ,Materials science ,Magnetic domain ,Condensed matter physics ,Field (physics) ,Magnetoresistance ,Physics ,Nanowire ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Vortex state ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Magnetization ,0103 physical sciences ,0210 nano-technology ,Line (formation) - Abstract
We studied the magnetoresistance of symmetric cobalt nanorings with nanowires attached at diametrically opposite positions. Deterministic switching, induced by an external magnetic field between the stable magnetization states, is demonstrated using histograms of the resistance changes as a function of an external magnetic field. The changes of the switching fields were studied as the lateral dimensions of these elements were varied systematically. The field required to switch between the vortex state and the onion state of the rings decreases as the line widths of the elements were increased. The vortex state is unstable at the larger line widths. Our experimental observations are explained using micromagnetic simulations.
- Published
- 2016
246. Systematic study of magnetization reversal in beaded fibers from different magnetic materials.
- Author
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Amini, Fedi, Blachowicz, Tomasz, and Ehrmann, Andrea
- Subjects
- *
MAGNETIC materials , *MAGNETIZATION reversal , *FIBERS , *MAGNETIC properties , *ANGULAR distribution (Nuclear physics) , *MAGNETIC fields - Abstract
• Beaded nanofibers made from magnetic materials showed magnetization reversal via a vortex state. • Coercive fields and saturation fields showed similar angle-dependencies for all materials. • The angle dependence of magnetic properties suggests a defined angular distribution in nanofibers. Electrospun nanofibers produced from magnetic materials form a magnetic network which may be used for neuromorphic computing and other novel applications. While the influence of bending radii on the magnetization reversal in such nanofibers was already discussed in the literature, the often occurring beads along the fibers have not yet been investigated in detail. It can be assumed that such beads will support domain wall formation due to a reduction of the relative impact of the shape anisotropy, in this way influencing magnetization reversal along the fiber. Here, we simulate magnetization reversal processes in iron, nickel, cobalt and magnetite fibers with a bead in the middle, produced in three typical dimensions gained by electrospinning. In most cases a vortex state occurs during magnetization reversal, independent from the material and the dimensions. For some angular orientations of the external magnetic field, double-vortex or meander states are visible, usually also followed by vortex states. These simulations underline the strong and highly reliable impact of beads along electrospun fibers, making these structures useful for data storage, transport and other applications. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
247. On the vortex matter in a two-band superconducting meso-prism.
- Author
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Aguirre, C.A., Joya, M.R., and Barba-Ortega, J.
- Subjects
- *
PRISMS , *BOSE-Einstein condensation , *MAGNETIC susceptibility , *VORTEX motion , *MAGNETIC fields , *SUPERCONDUCTORS , *GROSS-Pitaevskii equations - Abstract
• Spontaneous generation of anti-vortices, due to the oscillations of the crystalline network. • Found a novel and interesting behavior in the vorticity • Two component superconductor • In-homogeneous systems We solve the two-band Ginzburg-Landau equations for a superconducting mesoscopic prism for a condensate characterized by two order parameters (ψ 1 , ψ 2). We study the effect of the phase and γ ˜ differences on the vortex state, magnetization, magnetic susceptibility (χ m) , vortex localization, and vorticity for boths condensate. Finally, we present shown how the vortices form conglomerates in the superconductor sample states of fractional vorticity in the system for different external magnetic fields. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
248. p-Wave Superconductors in Sr2RuO4 and Bechgaard Salts.
- Author
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Maki, K., Wang, G.-f., and Won, H.
- Abstract
We review our recent works on the vortex state in p-wave superconductors. First, in a magnetic field parallel to the c-axis, the square vortex lattice is most stable, except in the immediate vicinity of T = T
c0 . Second, the effect of impurities on Hc2 is studied, which exhibits characteristics of unconventional superconductors. Finally, the a– b anisotropy in the upper critical field in a magnetic field is considered. This anisotropy provides important information about the fourfold term arising from the Fermi surface effect. [ABSTRACT FROM AUTHOR]- Published
- 1999
- Full Text
- View/download PDF
249. Field Dependence of the Vortex Structure in d-Wave and s-Wave Superconductors.
- Author
-
Ichioka, Masanori, Hasegawa, Akiko, and Machida, Kazushige
- Abstract
The vortex structure and its field dependence are studied in the clean limit on the basis of the quasi-classical Eilenberger theory to find their difference between $$d_{x^2 - y^2 }$$ - and s-wave pairings. We show the $$d_{x^2 - y^2 }$$ -wave nature and the vortex lattice effect on the local density of states around the vortex, and on the field dependence of the spatially averaged density of states. The $$d_{x^2 - y^2 }$$ -wave pairing introduces a fourfold symmetric structure around each vortex core in the pair potential and the internal field. With increasing field, their contribution becomes significant to the whole structure of the vortex lattice state. [ABSTRACT FROM AUTHOR]
- Published
- 1999
- Full Text
- View/download PDF
250. Exactly Aligned Magnetic Field and the Fulde–Ferrell–Larkin–Ovchinnikov State in Quasi-Low-Dimensional Superconductors.
- Author
-
Shimahara, Hiroshi
- Abstract
In quasi-low-dimensional type II superconductors, the orbital pair-breaking effect is considerably reduced when the magnetic field is exactly aligned in a direction parallel to the highly conducting layer. Then, since the superconducting phase survives up to a very high magnetic field comparable to the Pauli-paramagnetic limit, we could expect some drastic phenomena, such as the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state. In this paper, we discuss the condition of the tilt angle for the appearance of the FFLO state, and also discuss the stable spatial structure of the FFLO state. Further, we show an example of a quasi-two-dimensional system in which the FFLO state is remarkably enhanced, that is, a two-dimensional tight binding system of appropriate hole concentrations. [ABSTRACT FROM AUTHOR]
- Published
- 1999
- Full Text
- View/download PDF
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