Single Domain Wall Propagation Research Articles

Effect of Magnetostatic Interaction on the Single-Domain Wall Propagation in Magnetic Microwires

Effect of Magnetostatic Interaction on the Single-Domain Wall Propagation in Magnetic Microwires

Controlling of the single domain wall propagation in magnetic microwires by magnetostatic interaction

Ultrafast magnetization switching through the single domain wall (DW) propagation has been reported in amorphous micrometric and submicrometric wires. However the performance of prospective devices utilizing DW propagation is determined by the degree to which DW propagation can be controlled. In this article, we propose a novel method for effectively controlling the single DW propagation in a specially designed array consisting of two magnetic microwires by the stray field from magnetically softer microwires. We have experimentally demonstrated that the DW velocity of magnetically harder Fe-rich microwire in such a linear array is affected by the stray field of magnetically softer Co-rich microwire. Additionally, the domain wall can be trapped in the Fe-rich microwire by the stray field produced by the Co-rich microwire in such a linear array. The observed effect of magnetostatic interaction depends on the position of the Co-rich microwire in such a linear array. Controllable domain wall propagation observed in such a linear array can be a useful tool for simple and more flexible ways of controllable trapping and braking of single DWs in Fe-rich microwires showing spontaneous magnetic bistability.

Matteucci Effect and Single Domain Wall Propagation in Bistable Microwire under Applied Torsion

Systematic experimental results on the Matteucci effect in torsioned magnetostrictive FeSiB microwire are introduced, observed during the propagation of a single domain wall (DW) under the action of axial driving magnetic field, Hdr. These data are discussed, reviewing current bibliography models and proposing new perspectives. The unidirectional DW velocity is quantified by voltage induced in tiny pickup coils along the microwire. The Matteucci electromotive force (emf) induced between the microwire's ends is associated with depinning and annihilation of the DW, introducing a new method to measure DW velocity. The emf amplitude is proportional to the DW velocity and the time derivative of the azimuthal magnetization, tailored by applied torsion. The data confirm the existence of net values of azimuthal magnetization and spontaneous torsion induced during fabrication. The clockwise/counterclockwise applied torsion dependence of Matteucci emf and DW velocity are experimentally determined for parallel and antiparallel Hdr. Asymmetric behaviors are observed for both, the sense of applied torsion and the direction of Hdr. The experimental data are discussed in terms of the magnetoelastic anisotropy introduced by torsion. Through analysis of the DW dynamics, such asymmetric behaviors are interpreted as a magnetochiral effect derived from the change of chirality of the propagating wall.

Magnetic Microwires with Unique Combination of Magnetic Properties Suitable for Various Magnetic Sensor Applications.

There is a pressing demand to improve the performance of cost-effective soft magnetic materials for use in high performance sensors and devices. Giant Magneto-impedance effect (GMI), or fast single domain wall (DW) propagation can be observed in properly processed magnetic microwires. In this paper we have identified the routes to obtain microwires with unique combination of magnetic properties allowing observation of fast and single DW propagation and GMI effect in the same microwire. By modifying the annealing conditions, we have found the appropriate regimes allowing achievement of the highest GMI ratio and the fastest DW dynamics. The observed experimental results are discussed considering the radial distribution of magnetic anisotropy and the correlation of GMI effect, and DW dynamics with bulk and surface magnetization processes. Studies of both Fe- and Co-rich microwires, using the magneto-optical Kerr effect, MOKE, provide information on the magnetic structure in the outer shell of microwires. We have demonstrated the existence of the spiral helical structure in both studied microwires. At the same time, torsion mechanical stresses induce helical bistability in the same microwires, which allow us to consider these microwires as materials suitable for sensors based on the large Barkhausen jump.

Single Domain Wall Propagation in 2D Magnetic Nano-traps Under Field Pulses

Various domain wall traps were designed, patterned and exploited by means of Lorentz microscopy and magnetic simulation. Those structures consist of two straight nanowires and connecting pads with ...

Engineering of magnetic properties and domain wall dynamics in Fe-Ni-based amorphous microwires by annealing

We present experimental studies related to the influence of annealing on domain wall (DW) dynamics and magnetic hysteresis of Fe-Ni-rich microwires. As-prepared and annealed Fe62Ni15.5Si7.5B15 and Fe49.6Ni27.9Si7.5B15 microwires present perfectly rectangular hysteresis loops and single DW propagation. DW velocity, v, DW mobility, S, and coercivity, Hc, of both studied microwires have been considerably affected after annealing. In Fe62Ni15.5Si7.5B15 microwires, we observed a gradual S increase with annealing time, tann, increasing. However, a non-monotonic S (tann) dependence was observed in Fe49.6Ni27.9Si7.5B15 microwires. We discussed observed dependencies in terms of different magnetoelastic anisotropy, domain walls stabilization, and different Curie temperatures of studied microwires.

Engineering of Magnetic Properties of Co- and Fe-Rich Microwires

We present our experimental results on optimization of the magnetic softness, domain wall (DW) dynamics, and giant magnetoimpedance (GMI) effect of Fe- and Co-rich microwires. It is found that the as-prepared Co-rich microwires possess much higher GMI effects and linear hysteresis loop. On the other hand, the magnetic softness and GMI effect of Fe-rich microwires can be improved by stress annealing. In addition, the DW velocity of the microwires can be considerably improved by annealing. The single DW propagation can also be observed in properly annealed Co-rich microwires. These observed dependencies can be attributed to the relaxation of internal stresses after annealing and the interplay of compressive stresses and axial internal stresses after stress annealing.

Manipulation of fast magnetization switching in magnetically bistable microwires through the magnetoelastic anisotropy

IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, SpainWe studied effect of magnetoelastic anisotropy and role of defects on domain wall (DW) dynamics andremagnetization process of magnetically-bistable microwires. We manipulated the magnetoelastic anisotropychanging the ratio between the metallic nucleus diameter and glass coating thickness and applying the tensilestresses. Application of stresses resulted in increase of the switching field and decrease of the DW velocity, v. Therole of defects existing in magnetically bistable microwires is related with nucleation of new reversed domains.Abrupt jumps on v(H) dependences correlate with defects existing in microwires. Annealing allows considerablyincrease DW velocity, enhances the magnetic field range of single DW propagation regime and domain wall mobility.Key words: amorphous microwires, domain wall dynamics, magnetic anisotropy1. IntroductionStudies of domain wall (DW) propagation in thinmagnetic wires prepared by different methods attractedgrowing attention during last few years [1, 2]. Maintechnological interest is related with proposedapplications involving the information storage,magnetic sensors and logics. For aforementionedapplications the DW speed and the ways for the DWdynamics manipulation are essentially relevant.Reported DWs propagation can be driven by themagnetic field as well as by the electric current flowingthrough the sample. The DW velocity is determined bythe magnetic field value as well as by the shape anddimensions of the wires [1, 3-6]. Thus, for amorphousmicrometric wires with circular cross section fastest DWvelocity (exceeding 1000 m/s) have been reported [7,8].Additionally the DW velocity, v, depends on themagnetoelastic anisotropy depending on themagnetostriction constant value as well as on theinternal or applied stress [9]. On the other hand, forcontrolling the DWs dynamics in thin wires (either withrectangular or cylindrical cross-section), fewmechanisms involving the DW injection, creation ofartificial defects and inhomogeneities, controllable DWcollision etc have been reported [9, 10].Studies of glass-coated microwires withferromagnetic nucleus attracted considerable attentionwithin last few years owing to their reduced dimensionsand unusual soft magnetic properties such asspontaneous magnetic bistability, Giantmagnetoimpedance effect and high magneticpermeability. Magnetic bistability is related with largeand single Barkhausen jump observed in amorphousmicrowires with positive magnetostriction constant isparticularly interesting for studies of the DWpropagation within the inner core of microwire [5-7, 11].On the other hand giant magneto-impedance, GMI,effect and extremely soft magnetic properties can beuseful for magnetic sensors applications [12, 13].Abovementioned magnetic bistability observed inamorphous glass-coated microwires with positivemagnetostriction constant is related with fastmagnetization switching of a large single axiallymagnetized domain by fast DW propagation of a singleDW [5-8, 11, 13]. Therefore these microwires are uniquematerial allowing studying the magnetization dynamicsof a single DW in a cylindrical micrometric wire.Appearance of such peculiar domain structureconsisting of a large single axially magnetized domainsurrounded by outer radially magnetized shell isdetermined by the stresses arising during rapidsolidification of composite thin wire [5, 13-17]. Thestrength of these stresses originated from the differencein thermal expansion coefficients of the metal and glassis determined by the volumes of metallic nucleus andglass coating [14-16]. Consequently the magneticsoftness of glass-coated microwires is determined by themagnetoelastic anisotropy originated from thecomposite character being also depending on themetallic nucleus composition and ratio between themetallic nucleus diameter, and total microwirediameter.Consequently fast magnetization switching ofmicrowires is related with the propagation of the singlehead-to head DW along the wire.Recently we reported, that the samplesinhomogeneities, observed through the measurementsof the distribution of the local nucleation fields, H

Fast magnetization switching in Fe-rich amorphous microwires: Effect of magnetoelastic anisotropy and role of defects

We studied effect of magnetoelastic anisotropy and role of defects on domain wall (DW) dynamics and remagnetization process of magnetically-bistable Fe-rich microwires. We manipulated the magnetoelastic anisotropy applying the tensile stresses. Application of stresses resulted in decrease of the DW velocity v, and DW mobility S. Consequently, we observed certain correlation between the magnetoelastic energy and DW dynamics in microwires: decreasing the magnetoelastic energy, Kme, DW velocity can be increased. We are trying to reveal contribution of local defects on DW propagation in amorphous microwires. Below some critical magnetic field, Hn, determined by the microwires inhomogeneities, almost linear DW velocity, v on magnetic field, H, dependence is found. When the applied magnetic field exceeds Hn, new reverse domains can be nucleated and consequently tandem remagnetization mechanism can be realized. The role of defects existing in magnetically bistable microwires is related with nucleation of new reversed domains. Abrupt jumps on v(H) dependences correlate with defects existing in microwires. Magnetic field value, corresponding to such jump on v(H) dependences, correlates with the minimum nucleation field, which determines threshold between single and multiple domain wall propagation regimes. In the latter case, under the action of the magnetic field, a new domain can be spontaneously nucleated in front of the propagating head-to-head closure domain. In this way real structure of microwires limits single DW propagation regime.

Single-Domain Wall Propagation and Damping Mechanism during Magnetic Switching of Bistable Amorphous Microwires

The mechanism of nucleation and propagation of a single-domain wall is studied as a function of temperature in bistable Fe-based amorphous microwire with a unique simple domain structure. An extended nucleation-propagation model is proposed with a negative nucleation field. From quantitative analysis of the propagating wall characteristics, a new damping is theoretically introduced as arising from structural relaxation which dominates in the low temperature regime.