Magnetic Wires Research Articles

Current-induced dynamics of bubble domains in perpendicularly magnetized TbFeCo wires

We investigated the bubble-domain dynamics in TbFeCo wires with perpendicular magnetization under electric current flows. In TbFeCo wires with relatively low saturation magnetization (Ms), the current pulse caused the bubble domains to collapse without moving. In TbFeCo wires with relatively high Ms, however, the bubble domains grew in the current direction. We explain these shape changes by assessing the Ms-dependent forces caused by the exchange field and magnetostatic field. We also found that we could control the current-induced behaviors of the bubble domains by using an external magnetic field.

High-Frequency Electric Properties of Amorphous Soft Magnetic Cobalt-Based Alloys in the Region of Transition to the Paramagnetic State

Effect of the temperature on the high-frequency electric impedance of amorphous soft magnetic cobalt-based wires is investigated. A high sensitivity of their impedance to the transition of the ferromagnetic state into the paramagnetic state is demonstrated. The temperature dependences of the impedance measured at different alternating current frequencies allow a distribution of the magnetic phases in the wire volume to be elucidated.

Dynamic Trajectory and Capture of Fine Dust by Magnetic Mesh Filters Based on a Particle Velocity Model

The particle velocity model developed in this study described the dynamic motion of fine dust particles along the magnetized mesh wires in a low Stokes regime. The numerically evaluated velocity contour of the particles modeled the critical path lines indicating the threshold positions for magnetic collection. The velocity contour was determined using the parameters such as particle size, magnetic intensity, flow velocity, and mesh configuration including wire thickness and packing density. Particle size was one of the most significant parameters to determine the magnetic collection. The theoretical estimation matched well with the lab experiments, but the discrepancy increased for large particles with a fine filter. In consequence, application of magnetized mesh filters could contribute to the collection of the ferromagnetic dust or aerosols to a certain extent without any additional power or pressure resistance.Copyright 2015 American Association for Aerosol Research

Traveling pulse on a periodic background in parametrically driven systems.

Macroscopic systems with dissipation and time-modulated injection of energy, parametrically driven systems, can self-organize into localized states and/or patterns. We investigate a pulse that travels over a one-dimensional pattern in parametrically driven systems. Based on a minimal prototype model, we show that the pulses emerge through a subcritical Andronov-Hopf bifurcation of the underlying pattern. We describe a simple physical system, a magnetic wire forced with a transverse oscillatory magnetic field, which displays these traveling pulses.

Matrix theory of wave propagation in hybrid electric/magnetic multiwire transmission line systems

Matrix methods to deal with multimodal propagation in electric multiwire transmission lines are quite well known. However, the matrix theory of magnetic multiwire transmission lines (MMTL) has been established only very recently. In this study, we advance the new subject of hybrid electric and MMTL, which has never been addressed in the literature. A complex system composed of N + 1 electric wires and n + 1 magnetic wires is theoretically analyzed from the viewpoint of their interaction/coupling, transmission line matrix equations, ABCD matrix formalism, and superposition of propagation modes.

Shaping micron-sized cold neutron beams

In the field of neutron scattering, the need for micro-sized (1–50µm) thermal or cold neutron beams has recently appeared, typically in the field of neutron imaging to probe samples with a high spatial resolution. We discuss various possibilities of producing such micro-sized neutron beams. The advantages and drawbacks of the different techniques are discussed. We show that reflective optics offers the most flexible way of producing tiny neutron beams together with an enhanced signal to background ratio. The use of such micro beams is illustrated by the study of micrometric diameter magnetic wires.

Engineering Magnetic Domain-Wall Structure in Permalloy Nanowires

Nanoscale magnetic wires are of importance for potential data storage and processing technologies. In such wires magnetic domain walls, the regions separating opposite magnetic orientations, could be used as the basis of a high-speed, nonvolatile ``universal memory.'' The authors use a finely focused beam of gallium ions to demonstrate controlled modification of material properties leading to the controllable trapping and type selection of domain walls, a key step toward this technological goal.

Electrochemically synthesized polyethylene glycol coated ferromagnetic nanowire arrays

Polyethylene glycol (PEG) coated Fe, Co, and Ni nanowires (NWs) were fabricated by a template assisted electrochemical deposition method. In this process, polymer and metal ions were deposited simultaneously at room temperature. The effects of different pore diameters of the anodized aluminum oxide (AAO) templates, concentration of electrolytes, and applied current on the growth of the magnetic wires were studied. The polycrystalline polymer-coated ferromagnetic-nanowire arrays were found to have high coercivity with PEG not affecting the magnetic properties. Relative to uncoated metal nanowires, the outer polymer coating strengthens high aspect ratio wires, preventing them from breaking as easily.

Dicopper(II) metallacyclophanes as multifunctional magnetic devices: a joint experimental and computational study.

Metallosupramolecular complexes constitute an important advance in the emerging fields of molecular spintronics and quantum computation and a useful platform in the development of active components of spintronic circuits and quantum computers for applications in information processing and storage. The external control of chemical reactivity (electro- and photochemical) and physical properties (electronic and magnetic) in metallosupramolecular complexes is a current challenge in supramolecular coordination chemistry, which lies at the interface of several other supramolecular disciplines, including electro-, photo-, and magnetochemistry. The specific control of current flow or spin delocalization through a molecular assembly in response to one or many input signals leads to the concept of developing a molecule-based spintronics that can be viewed as a potential alternative to the classical molecule-based electronics. A great variety of factors can influence over these electronically or magnetically coupled, metallosupramolecular complexes in a reversible manner, electronic or photonic external stimuli being the most promising ones. The response ability of the metal centers and/or the organic bridging ligands to the application of an electric field or light irradiation, together with the geometrical features that allow the precise positioning in space of substituent groups, make these metal-organic systems particularly suitable to build highly integrated molecular spintronic circuits. In this Account, we describe the chemistry and physics of dinuclear copper(II) metallacyclophanes with oxamato-containing dinucleating ligands featuring redox- and photoactive aromatic spacers. Our recent works on dicopper(II) metallacyclophanes and earlier ones on related organic cyclophanes are now compared in a critical manner. Special focus is placed on the ligand design as well as in the combination of experimental and computational methods to demonstrate the multifunctionality nature of these metallosupramolecular complexes. This new class of oxamato-based dicopper(II) metallacyclophanes affords an excellent synthetic and theoretical set of models for both chemical and physical fundamental studies on redox- and photo-triggered, long-distance electron exchange phenomena, which are two major topics in molecular magnetism and molecular electronics. Apart from their use as ground tests for the fundamental research on the relative importance of the spin delocalization and spin polarization mechanisms of the electron exchange interaction through extended π-conjugated aromatic ligands in polymetallic complexes, oxamato-based dicopper(II) metallacyclophanes possessing spin-containing electro- and chromophores at the metal and/or the ligand counterparts emerge as potentially active (magnetic and electronic) molecular components to build a metal-based spintronic circuit. They are thus unique examples of multifunctional magnetic complexes to get single-molecule spintronic devices by controlling and allowing the spin communication, when serving as molecular magnetic couplers and wires, or by exhibiting bistable spin behavior, when acting as molecular magnetic rectifiers and switches. Oxamato-based dicopper(II) metallacyclophanes also emerge as potential candidates for the study of coherent electron transport through single molecules, both experimentally and theoretically. The results presented herein, which are a first step in the metallosupramolecular approach to molecular spintronics, intend to attract the attention of physicists and materials scientists with a large expertice in the manipulation and measurement of single-molecule electron transport properties, as well as in the processing and addressing of molecules on different supports.

Designing an optimum pulsed magnetic field by a resistance/self-inductance/capacitance discharge system and alignment of carbon nanotubes embedded in polypyrrole matrix.

In this work, an optimized pulsed magnetic field production apparatus is designed based on a RLC (Resistance/Self-inductance/Capacitance) discharge circuit. An algorithm for designing an optimum magnetic coil is presented. The coil is designed to work at room temperature. With a minor physical reinforcement, the magnetic flux density can be set up to 12 Tesla with 2 ms duration time. In our design process, the magnitude and the length of the magnetic pulse are the desired parameters. The magnetic field magnitude in the RLC circuit is maximized on the basis of the optimal design of the coil. The variables which are used in the optimization process are wire diameter and the number of coil layers. The coil design ensures the critically damped response of the RLC circuit. The electrical, mechanical, and thermal constraints are applied to the design process. A locus of probable magnetic flux density values versus wire diameter and coil layer is provided to locate the optimum coil parameters. Another locus of magnetic flux density values versus capacitance and initial voltage of the RLC circuit is extracted to locate the optimum circuit parameters. Finally, the application of high magnetic fields on carbon nanotube-PolyPyrrole (CNT-PPy) nano-composite is presented. Scanning probe microscopy technique is used to observe the orientation of CNTs after exposure to a magnetic field. The result shows alignment of CNTs in a 10.3 Tesla, 1.5 ms magnetic pulse.

Investigation of domain wall motion in RE-TM magnetic wire towards a current driven memory and logic

Current driven magnetic domain wall (DW) motions of ferri-magnetic TbFeCo wires have been investigated. In the case of a Si substrate, the critical current density (Jc) of DW motion was successfully reduced to 3×106A/cm2. Moreover, by using a polycarbonate (PC) substrate with a molding groove of 600nm width, the Jc was decreased to 6×105A/cm2. In order to fabricate a logic in memory, a current driven spin logics (AND, OR, NOT) have been proposed and successfully demonstrated under the condition of low Jc. These results indicate that TbFeCo nanowire is an excellent candidate for next generation power saving memory and logic.

ファンモータ用小型三相誘導電動機の電磁振動に関する数値解析による検証（巻線仕様による電磁振動の低減）

ファンモータ用小型三相誘導電動機の電磁振動に関する数値解析による検証（巻線仕様による電磁振動の低減）

Tunable permeability of magnetic wires at microwaves

This paper presents the analysis into microwave magnetic properties of magnetic microwires and their composites in the context of applications in wireless sensors and tunable microwave materials. It is demonstrated that the intrinsic permeability of wires has a wide frequency dispersion with relatively large values in the GHz band. In the case of a specific magnetic anisotropy this results in a tunable microwave impedance which could be used for distributed wireless sensing networks in functional composites. The other range of applications is related with developing the artificial magnetic dielectrics with large and tunable permeability. The composites with magnetic wires with a circumferential anisotropy have the effective permeability which differs substantially from unity for a relatively low concentration (less than 10%). This can make it possible to design the wire media with a negative and tunable index of refraction utilising natural magnetic properties of wires.

Domain Wall Propagation in Co-Based Glass-Coated Microwires: Effect of Stress Annealing and Tensile Applied Stresses

RECENTLY, domain wall (DW) propagation in magnetic wires has been recognized as one of the important lines of research due to its potential use in magnetic devices [1]–[7]. The DW speed and the possibilities for the DW dynamics manipulation are quite relevant for these applications. Extremely fast DW propagation has been reported for amorphous magnetically bistable microwires with positive magnetostriction constant λs and circular cross section (usually, exceeding 1000 m/s) [3], [4]. On the other hand, ferromagnetic glass-coated microwires have attracted growing attention in the last few years, mostly owing to their outstanding soft magnetic properties (magnetic bistability, enhanced magnetic softness, Giant magnetoimpedance (GMI) effect, and fast DW propagation) [5]–[7]. These microwires have a composite character consisting of a cylindrical metallic nucleus of (1–30 μm) and glass coating (with thickness of 1–20 μm). These microwires can be prepared by the modified Taylor–Ulitvosky technique, which involves simultaneous rapid quenching and drawing of the metallic nucleus inside a glass capillary [6], [7]. Thus, strong stresses are introduced in the metallic nucleus arising from the drawing and quenching, as well as from the different thermal expansion coefficient between the glass sheath and the metallic nucleus [5], [6], [8]–[10]. Therefore, the magnetoelastic anisotropy induced by the internal stresses plays an important role in controlling their magnetic properties [4], [5], [7]–[9]. Fe-rich microwires with positive magnetostriction coefficient, λs , present magnetic bistability related to a large and single axially magnetized inner core. Therefore, one can observe quite fast magnetization switching within the single magnetic domain related with fast DW propagation. In particular, these materials are unique for studying the DW propagation since they can exhibit a very fast DW velocity [2]–[4], [6], [11]. On the other hand, it is well known that the DW dynamics in glasscoated microwires is strongly dependent to external parameters

Magnetization Reversal of Disorder-Induced Ferromagnetic Regions in Fe<sub>60</sub>Al<sub>40</sub> Thin Films

Magnetization processes were investigated by employing magnetometry and magnetic domain imaging using magnetooptical longitudinal and polar effects in Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">40</sub> films of 40 nm thickness. The films were initially chemically ordered and weakly ferromagnetic, and a large increase in the saturation magnetization was achieved through chemical disorder induced by Ne <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -ion irradiation. Various sample geometries were investigated: 1) continuous film; 2) homogenously irradiated wire; and 3) magnetic stripe-patterned wire. Magnetization reversal and magnetic domains formed under the influence of the above sample geometries are reported.

Parametric controls on giant magnetoimpedance (GMI) behaviour of CoFeSiBCr amorphous wires for prospective sensor applications

Investigation is focused on the effect of different parametric controls like driving frequency, amplitude of the alternating current (ac), direct current (dc) bias field and anisotropy field (Hk) on the Giant Magneto-Impedance (GMI) properties of rapidly quenched soft magnetic Co66Fe2Si13B15Cr4 amorphous wires developed by in-water quenching technique. Optimal controls of these parameters like driving frequency and amplitude of the ac were found to display a sensitive change in GMI properties at optimal frequency of 5MHz and 5mA driving current. The influence of these controls on the output factors like maximum GMI ratio (GMImax), transition from single peak (SP) to double peak (DP), field sensitivity of GMI (η) and anisotropy field (Hk) throw light on the application of the developed wires for sensors. In addition to high Hk, driving frequency of 5MHz also delivered a combination of desirable sensor properties like high level of sensitivity and its enhanced span of stability. Joule heating further improved the GMI response of the material through current annealing at a current density of 5A/mm2.

Tracking the individual magnetic wires' switchings in ferromagnetic nanowire arrays using the first-order reversal curves (FORC) diagram method

The complex hysteretic properties observed in structured ferromagnetic materials can be revealed with remarkable details in magnetization processes like the first-order reversal curves (FORC) – a characterization technique extensively used in recent years. The really fundamental problem in the analysis of experimental FORC diagrams is related to the possibility to link the hysteretic properties of real physical entities in a unique way with regions from the FORC distributions. Actually, what many scientists are often doing is to use a Preisach-type interpretation of FORC data without a proof for the accuracy of this procedure. In this paper we analyze in detail the relation between the switching events of physical entities given by the Preisach function and the FORC distribution in magnetic nanowire arrays with the aim to show the limits of the conventional interpretation of FORC data. For this type of sample we show how the real switching events are contributing to the experimental diagram. We present in a systematic manner the way in which the switchings of the physical wires are observed multiple times (both as positive or negative contributions). The multiplicity of switching occurrences is not the same for all the wires in the sample, being dependent on the wire intrinsic coercivity and its position in the array. In this manner one can track the switchings contributions of real magnetic wires on the FORC diagram.

Soliton–antisoliton interaction in a parametrically driven easy-plane magnetic wire

Abstract In the present work we study the soliton–antisoliton interaction in an anisotropic easy-plane magnetic wire forced by a transverse uniform and oscillatory magnetic field. This system is described in the continuous framework by the Landau–Lifshitz–Gilbert equation. We find numerically that the spatio-temporal magnetization field exhibits both annihilative and repulsive soliton–antisoliton interactions. We also describe this system with the aim of the associated Parametrically Driven and Damped Nonlinear Schrodinger amplitude equation and give an approximate analytical solution that roughly describes the repulsive interaction.

Vanadium Sandwich Complexes with Boroxine and Boronyl Boroxine Ligands

AbstractA DFT investigation on half‐sandwich‐type C3v B3O3X3V, full‐sandwich‐type D3d [B3O3X3]2V, and triple‐decker complexes [B3O3X3]3V2 (X = H, BO) containing B3O3H3 or B3O3(BO)3 ligands were performed. Both B3O3H3 and B3O3(BO)3 units serve as robust inorganic ligands in B3O3X3V, [B3O3X3]2V, and [B3O3X3]3V2 complex series. Effective d–π coordination interactions between the partially filled 3d orbitals of the transition‐metal center and the delocalized π orbitals of the B3O3X3 ligands maintain the stabilities of the complexes. The largest contributions to the orbital interactions in the B3O3X3V, [B3O3X3]2V, and [B3O3X3]3V2 complexes come from the V → B3O3X3 δ back donation. The thermodynamic stabilities and magnetic properties of these complexes were also investigated. These magnetic complexes were found to be particularly stable with respect to their reaction energy. The sandwich structural pattern developed in this work expands the structural domain of transition‐metal complexes by introducing inorganic B3O3H3 and B3O3(BO)3 into traditional sandwich‐type structures, and this pattern may be extended to [B3O3X3]nVn–1 sandwiches (n ≥ 4), which could act as linear magnetic wires.

Nanoscale imaging and control of domain-wall hopping with a nitrogen-vacancy center microscope.

The control of domain walls in magnetic wires underpins an emerging class of spintronic devices. Propagation of these walls in imperfect media requires defects that pin them to be characterized on the nanoscale. Using a magnetic microscope based on a single nitrogen-vacancy (NV) center in diamond, we report domain-wall imaging on a 1-nanometer-thick ferromagnetic nanowire and directly observe Barkhausen jumps between two pinning sites spaced 50 nanometers apart. We further demonstrate in situ laser control of these jumps, which allows us to drag the domain wall along the wire and map the pinning landscape. Our work demonstrates the potential of NV microscopy to study magnetic nano-objects in complex media, whereas controlling domain walls with laser light may find an application in spintronic devices.