Our recent publications

2017

S. Trummer, A. Ehrmann, A. Büsgen
Development of underwear with integrated 12 channel ECG for men and women
Autex Research Journal, online first (2017)

Abstract: Cardiovascular diseases are the most frequent cause of death worldwide. Cases of cardiac arrest can often be attributed to undetected cardiac arrhythmia. Detecting rare episodes of arrhythmia necessitates long-term ECG measurements along days or weeks. However, due to the relatively small number of electrodes used for these ECGs, abnormal episodes can still go unrecognized. This article thus describes the development of underwear with ten inbuilt textile ECG electrodes, allowing for the measurement of long-term 12-lead ECG. As against the constructs of other research groups, the position of electrodes offers the same detection directions as the common 12-lead ECG equipment in hospitals or medical practices. Long-term tests have shown the suitability of the sensory underwear variants for men and women to detect reliable ECG signals without disturbing the patients’ comfort.


E. Gsell, F. Heimlich, A. Ehrmann, M. O. Weber
Dependence of dry, wet and washing relaxation on knitted structures and fabric parameters
Industria Textila 68, 121-125 (2017)

Abstract: Understanding the relaxation processes of knitted fabrics is of importance for knitting companies as well as in basic research. This article examines the new approach of relating the relaxation processes to the percentages of stitches, tucks, and floats in weft knitted structures, showing that especially the number of tucks strongly influences the relaxation behavior, and depicts the correlation of the relaxation processes with the cover factor and the stitch density.


T. Blachowicz, A. Ehrmann, B. Mahltig
Magneto-optic measurements on uneven magnetic layers on cardboard
AIP Advances 7, 045306 (2017)

Abstract: Measurements of magnetic hysteresis loops by magneto-optic Kerr effect (MOKE) are usually performed on even surfaces which reflect the impinging laser beam without any disturbance. Alternatively, such measurements can be done on regularly structured samples, resulting in the possibility to investigate different diffraction orders who deliver different information about the magnetism in the magnetic particles. Rough magnetic surfaces, however, occur when rough substrates are coated with a magnetic layer, or when large magnetic particles are placed on a base material due to practical reasons. The article depicts the possibility to measure magnetic hysteresis loops on surfaces with a roughness about one order of magnitude higher than the light wavelength. This enables applied measurements of magnetic parameters on biological samples, textiles, irregular magnetic nanofibers etc.


I. Juhász Junger, S. V. Homburg, T. Grethe, A. Herrmann, J. Fiedler, A. Schwarz-Pfeiffer, T. Blachowicz, A. Ehrmann
Examination of the sintering process dependent properties of TiO2 on glass and textile substrates
Journal of Photonics for Energy 7, 015001 (2017)

Abstract: In recent years, the development of smart textiles has attracted great attention. Such textiles can contain small electrical devices, which need a power supply. Dye-sensitized solar cells, which can be produced from nontoxic, cheap, low-purity materials, could fill this purpose. However, to reach reasonable cell properties, sintering the TiO2 layer on the substrate is necessary. Unfortunately, only a few textile materials can withstand a sintering process at high temperatures. Therefore, it is important to find an optimal temperature leading to a reasonable improvement of the cell characteristics without damaging the textile substrate. The influence of the sintering temperature on different properties is investigated. For this, the surface properties of the TiO2 coating, such as adhesion to the substrate, dye adsorption characteristic, and film stability, are investigated on different substrates, i.e., a glass plate, a stainless steel nonwoven fabric, and a carbon woven fabric. Two commercially available TiO2 sources are used: a TiO2 dispersion obtained from Man Solar and a water-based solution of TiO2 particles purchased from Kronos. The influence of the sintering temperature on short-circuit current and open-circuit voltage of solar cells on the aforementioned substrates is also examined.


I. Juhász Junger, S. V. Homburg, H. Meissner, T. Grethe, A. Schwarz-Pfeiffer, J. Fiedler, A. Herrmann, T. Blachowicz, A. Ehrmann
Influence of the pH value of anthocyanins on the electrical properties of dye-sensitized solar cells
AIMS Energy 5, 258-267 (2017)

Abstract: In recent years the harvesting of renewable energies became of great importance. This led to a rapid development of dye-sensitized solar cells which can be produced from low-purity materials. The best electrical properties are provided by cells prepared using synthetical, ruthenium based dyes. Unfortunately, most of them are toxic and expensive. The anthocyanins extracted for example from hibiscus flowers yield a more cost-effective and eco-friendly alternative to toxic dyes, however, with a loss of solar cell efficiency. In this article the possibility of improvement of the conversion efficiency by modification of the pH value of the dye is investigated. By decrease of the pH value, an increase of efficiency by a factor of two was achieved.


A. Ehrmann, T. Blachowicz
Interaction between magnetic nanoparticles in clusters
AIMS Materials Science 4, 383-390 (2017)

Abstract: Micromagnetic simulations are often used to model the magnetic properties of nanoparticles, depending on their shape and dimension as well as other parameters. Due to the significant increase in computing time for large-scale models, simulations are regularly restricted to a single magnetic nanoparticle. Applications in bit-patterned media etc., however, necessitate large clusters of nanostructures. In our recent works, the deviations of magnetic properties and magnetization reversal processes, comparing single nanoparticles and small clusters, were investigated using the micromagnetic simulation OOMMF. The studies concentrated on a special fourfold shape which has been shown before to offer four stable states at remanence, allowing for creating quaternary bit-patterned media with two bits storable in one position. The influence of downscaling was examined by varying the sample dimensions without changing the particle shape. The results show that in case of the special square nanostructures under investigation, the largest nanoparticles experience the strongest effect by being included in a cluster, while the technologically more relevant smaller nanoparticles have similar magnetic properties and identical magnetization reversal processes for single and clustered particles.


A. Popowicz, A. R. Kurek, T. Blachowicz, V. Orlov, B. Smolka
On the efficiency of techniques for the reduction of impulsive noise in astronomical images
Monthly Notices of the Royal Astronomical Society 463, 2172-2189 (2017)

Abstract: The impulsive noise in astronomical images originates from various sources. It develops as a result of thermal generation in pixels or the collision of cosmic rays with an image sensor, or it may be induced by high read-out voltage in an electron-multiplying CCD (EMCCD). It is usually efficiently removed by employing the dark frames or by averaging several exposures. Unfortunately, there are some circumstances when either the observed objects or positions of impulsive pixels evolve and, therefore, each image obtained has to be filtered independently. In this article we present an overview of impulsive noise filtering methods and compare their efficiency for astronomical image enhancement. The set of noise templates employed consists of dark frames obtained from CCD and EMCCD cameras working on the ground and in space. The experiments, conducted on synthetic and real images, allowed for drawing numerous conclusions about the usefulness of several filtering methods for various: (1) widths of stellar profiles, (2) signal-to-noise ratios, (3) noise distributions and (4) applied imaging techniques. The results of this evaluation are especially valuable for selecting the most efficient filtering schema in astronomical image-processing pipelines.


T. Blachowicz and A. Ehrmann
Micromagnetic investigation of low-symmetry 3D particles
IOP Conference Series: Materials Science and Engineering 175, 012057 (2017)

Abstract: Investigating the anisotropies of magnetic nanoparticles is crucial for further development of magnetic data storage media, MRAM, magnetic logical circuits, or magnetic quantum cellular automata. Former theoretical and experimental examinations have revealed the possibility to gain highly symmetric nanoparticles with increased numbers of magnetic states per storage element. In a recent project, we have investigated low-symmetry T-shaped 2D and 3D particles from iron using the micromagnetic simulation software MAGPAR which is based on solving the Landau-Lifshitz-Gilbert (LLG) equation of motion for a mesh built from tetrahedral finite elements. To examine the influence of the reduced symmetry, simulations were performed on the 3D double-T particle with the field applied in different directions in the x-y base plane, ranging from 0 to 180° in 5° steps. Additionally, the external magnetic field was rotated laterally under different angles with respect to the x-y plane, i.e. 5°, 22.5°, and 45°. Similar simulations were executed for the 2D single-T particle. Our results show the strong impact of the shape anisotropy and the respective possibility to tailor magnetic anisotropies according to the desired behaviour by modifying the nanoparticles' form.


M. Normann, T. Grethe, A. Schwarz-Pfeiffer, and A. Ehrmann
Development and characterization of textile batteries
IOP Conference Series: Materials Science and Engineering 175, 012058 (2017)

Abstract: During the past years, smart textiles have gained more and more attention. Products cover a broad range of possible applications, from fashion items such as LED garments to sensory shirts detecting vital signs to clothes with included electrical stimulation of muscles. For all electrical or electronic features included in garments, a power supply is needed - which is usually the bottleneck in the development of smart textiles, since common power supplies are not flexible and often not lightweight, prohibiting their unobtrusive integration in electronic textiles. In a recent project, textile-based batteries are developed. For this, metallized woven fabrics (e.g. copper, zinc, or silver) are used in combinations with carbon fabrics. The article gives an overview of our recent advances in optimizing power storage capacity and durability of the textile batteries by tailoring the gel-electrolyte. The gel-electrolyte is modified with respect to thickness and electrolyte concentration; additionally, the influence of additives on the long-time stability of the batteries is examined.



2016

A. Angelow, H. Bednorz, S. Böttcher, N. Schrader, A. Ehrmann
Optical differentiation between cashmere and other textile fibers by laser diffraction
Indian Journal of Fibre & Textile Research 41, 444-447 (2016)

Abstract: This paper reports a novel method to differentiate cashmere from synthetic fibres and even from other wool fibres with the help of laser diffraction patterns. In the diffraction pattern, only natural fibres depict additional spots above and below the actual diffraction plane. These spots can be used to distinguish different fibre materials by comparing their length-to-height aspect ratio with standard values. Especially, it can be recognized that the diffraction lines above and below the diffraction plane are significantly longer and finer for cashmere fibres than for any other wool.


A. Ehrmann and T. Blachowicz
Examination of Textiles with Mathematical and Physical Methods
Springer International Publishing, ISBN 978-3-319-47408-3 (E-book) / 978-3-319-47406-9 (Hardcover), 2016

About the book: This book presents basic knowledge on the examination of textile materials, from fibers to yarns and knitted or woven fabrics, using mathematical and physical methods. Besides typical textile test procedures, defined by well-known standards, the book aims at showing new ways to examine textile materials and giving an overview of the possibilities as well as problems occurring when methods from other areas are transferred into the examination of textiles. The contents range from apparently simple measurements, such as resistance of conductive coatings on woven fabrics, to diffraction measurements on woven fabrics, to optical examination of knitted fabrics by mathematical approaches to study yarn hairiness and cover factor.


N. Grimmelsmann, Y. Martens, P. Schäl, H. Meissner, A. Ehrmann
Mechanical and Electrical Contacting of Electronic Components on Textiles by 3D Printing
Procedia Technology 26, 66-71 (2016)

Abstract: Materials nowadays become smarter and “more intelligent”, containing novel functionalities or sensory components. In all areas of materials science, integrating new abilities into common materials belongs to the most important topics in research and development. In the textile area, several functions can be achieved by finishing techniques, i.e. physical and/or chemical modifications of textile surfaces. The integration of electronic components, however, still suffers from incompatibilities between soft, flexible, bendable textile fabrics and rigid electronic parts. Connecting conductive yarns with electronic components, such as SMD-LEDs etc., cannot be performed by soldering nor by sewing. The typical connection technologies of both areas fail in these cases. A new possibility to achieve such electrical and at the same time mechanical connections is given by 3D printing. In a recent project, we have studied chances and limitations of electric circuits combining textile fabrics with 3D printing. Textile fabrics were woven and knitted from common yarns as well as wires, strands and different conductive yarns. 3D printing was used to connect SMD elements and other small electronic parts with these base circuits and compared with soldered and sewn contacts. The influence of conductive wires, yarns or filaments integrated in the printed elements was tested. The article will give an overview of possibilities and problems in electrical contacting of small electronic components on partly conductive textile fabrics by conductive 3D printed connections. Additionally, an outlook to other potential areas of application, such as sensors and actuators on textile fabrics, is presented.


T. Blachowicz, A. Ehrmann
Simulation of magnetic coatings on textile fibers
Journal of Physics: Conference Series 738, 012057 (2016)

Abstract: While the properties of conductive fibres and coatings on textiles can easily be measured and calculated, magnetic coatings of fibres, yarns and fabrics still lack descriptions of their physical properties. Since magnetic textiles can be used for a variety of applications, from magnetic filters to invisible water-marks to magnetic coils and sensors, simulations would be supportive to understand and utilize their properties. The article gives an overview of different coatings on textile fibres, varying the magnetic materials as well as the fibre composition, giving rise to the interactions between neighbouring coated fibres. In this way, it is possible to understand the strong shape anisotropy which must be taken into account when the magnetic properties of textiles are to be tailored. Additionally, the differences between several possible magnetic coating materials become visible. This study can help adjusting the magnetic properties of textile fabrics to a desired application.


T. Blachowicz, A. Ehrmann
Stability of magnetic nano-structures with respect to shape modifications
Journal of Physics: Conference Series 738, 012058 (2016)

Abstract: Magnetic nano-structures can be used for various applications. Examinations of nano-structured systems often aim at decreasing pattern sizes due to their possible utilization in data storage media, in order to enhance the possible information density in a given area. This scaling process, however, is limited by the resolution of the lithography process which is used to produce the nano-particles. Thus the influence of shape modifications on the magnetic properties is important to be examined, especially the correlation between small form changes and magnetization reversal processes or coercive fields. In a recent project, square nanoparticles from permalloy were simulated using Magpar. Simulations were performed for the ideal geometric shape used in the lithography process, for the realistic shape of the produced nano-particles as obtained by SEM, and for intermediate steps between these extreme shapes. This study allows for estimation of the reliability of magnetic properties of nano-structures with respect to shape modifications in the lithography process.


S. Aumann, A. Ehrmann, M. O. Weber (Ed.)
Proceedings of 48th Conference of the International Federation of Knitting Technologists (IFKT), 8–11 June 2016, Moenchengladbach, Germany
IOP Conference Series: Materials Science and Engineering 141 (2016)

Preface: During June 09-10th 2016 the "48th International Congress of the International Federation of Knitting Technologists (IFKT)" coincided with IFKTs' 60th anniversary. The Congress was held together with the national conference of the Research Institute for Textile and Clothing from the Faculty of Textile and Clothing Technology, Mönchengladbach "MG Open Spaces" and the "Members' Conference of the Verein Deutscher Textilveredlungsfachleute (VDTF)" (an association of experts in the field of textile finishing). The whole event lasted from 09 until 11th June 2016 and took place in Mönchengladbach and Cologne, Germany. More than 220 people from universities, companies and other fields out of 15 different nations participated in the congress. The congress program consisted of seven keynote speakers, 45 oral presentations in 7 sections, 11 open spaces workshops in English and German, including a special workshop at Monforts' Advanced Technology Center (ATC) on "Knitting Concepts". Furthermore, a design showroom and a poster session were part of the program. This issue of the IOP Conference Series, Materials Science and Engineering (MSE), records papers of the Congress selected by the Congress Scientific Committee.


A. Schwarz-Pfeiffer, M. Obermann, M. O. Weber and A. Ehrmann
Smarten up garments through knitting
IOP Conference Series: Materials Science and Engineering 141, 012008 (2016)

Abstract: Smart textiles are a growing and fascinating field with enormous potential in the field of wearable electronics: shirts with integrated electrodes, socks stimulating the blood circulation or heating clothing are just a few examples of wearable, smart textile products. Most often, the technology of choice for on-the-body-worn smart textiles is knitting as it results in stretchable and, hence comfortable garments. This presentation explores the knitting technology in respect to smart textiles giving an overview of current research activities as well as commercially available products on the market. It further intends to foster the transfer of research approaches into business applications as well as to develop new challenging research ideas.


M. Obermann, M. Ellouz, S. Aumann, Y. Martens, P. Bartelt, M. Klöcker, T. Kordisch, A. Ehrmann and M. O. Weber
Non-destructive X-ray examination of weft knitted wire structures
IOP Conference Series: Materials Science and Engineering 141, 012007 (2016)

Abstract: Conductive yarns or wires are often integrated in smart textiles to enable data or energy transmission. In woven fabrics, these conductive parts are fixed at defined positions and thus protected from external loads. Knitted fabrics, however, have relatively loose structures, resulting in higher impacts of possible mechanical forces on the individual yarns. Hence, metallic wires with smaller diameters in particular are prone to break when integrated in knitted fabrics. In a recent project, wires of various materials including copper, silver and nickel with diameters varying between 0.05 mm and 0.23 mm were knitted in combination with textile yarns. Hand flat knitting machines of appropriate gauges were used to produce different structures. On these samples, non-destructive examinations, using an industrial X-ray system Seifert x|cube (225 kV) equipped with a minifocus X-ray tube, were carried out, directly after knitting as well as after different mechanical treatments (tensile, burst, and washing tests). In this way, structural changes of the stitch geometry could be visualized before failure. In this paper, the loop geometries in the knitted fabrics are depicted depending on knitted structures, wire properties and the applied mechanical load. Consequently, it is shown which metallic wires and yarns are most suitable to be integrated into knitted smart textiles.


N. Grimmelsmann, H. Meissner, A. Ehrmann
3D printed auxetic forms on knitted fabrics for adjustable permeability and mechanical properties
IOP Conference Series: Materials Science and Engineering 137, 012011 (2016)

Abstract: The 3D printing technology can be applied into manufacturing primary shaping diverse products, from models dealing as examples for future products that will be produced with another technique, to useful objects. Since 3D printing is nowadays significantly slower than other possibilities to manufacture items, such as die casting, it is often used for small parts that are produced in small numbers or for products that cannot be created in another way. Combinations of 3D printing with other objects, adding novel functionalities to them, are thus favourable to a complete primary shaping process. Textile fabrics belong to the objects whose mechanical and other properties can notably be modified by adding 3D printed forms. This article mainly reports on a new possibility to change the permeability of textile fabrics by 3D printing auxetic forms, e.g. for utilising them in textile filters. In addition, auxetic forms 3D printed on knitted fabrics can bring about mechanical properties that are conducive to tensile constructions.


A. Herrmann, J. Fiedler, A. Ehrmann, T. Grethe, A. Schwarz-Pfeiffer, T. Blachowicz
Examination of the sintering process dependent micro- and nanostructure of TiO2 on textile substrates
Proc. SPIE 9898, Photonics for Solar Energy Systems VI, 98980S (2016)

Abstract: Eco-friendly and sustainable power generation is one of the important aims of our time. Harvesting renewable energy can, e.g., be done by solar cells. For the integration in textiles, developing solar cells with typical textile haptics and pliability would be ideal. Additionally, textile solar cells should be created from low-purity materials in low-cost processes to be compatible with the textile industry. Thus, dye sensitized solar cells are ideal candidates for the integration of solar cell technology into textiles. In a recent project, we systematically test different material systems applied on textiles in which all functional layers are varied. One of the most crucial points is the sintering process of TiO2 which is only possible on a few textile materials. Additionally, the TiO2 coating itself contains the risk of being not completely isolating, allowing for dye and electrolyte or textile fibers penetrating through this layer and reaching the front electrode. This can result in short circuits or undesired counteracting voltages and currents. The article shows how different coating and sintering technologies of TiO2 on glass and textile fabrics influence the structures of the respective layers on different scales. It illustrates the differences between glass and textile fabrics in terms of the coating process and the resulting layer properties. Time-dependent measurements of open-circuit voltages and efficiencies show the physical implications of variations of the TiO2 layer structure and the resulting inner surfaces. In this way, we depict the different effects arising from undesired modifications of the TiO2 layer structure.


T. Blachowicz and A. Ehrmann
Stability of magnetic nano-structures against erroneous shape modifications
AIP Conf. Proc. 1727, 020004 (2016)

Abstract:Magnetic nano-structures can be used in various applications. Due to their possible utilization in data storage media, examinations of nano-structured systems often aim at decreasing the pattern size, in order to enhance the possible information density in a given area. Since this scaling process is limited by the resolution of the lithography process which is used to produce the nano-particles, it is important to determine the influence of erroneous shape modifications on the magnetic properties, such as magnetization reversal processes and coercive fields. For this, a square nano-wire system from permalloy has been simulated using Magpar. In a former work, changes of the wire diameter have been shown to result in different magnetization reversal mechanisms and significantly altered coercive fields. In a new project, the intersections of the wires – which are most susceptible to undesired shape modifications – have been changed by adding or subtracting parts. Additionally, the wire intersections have been separated step by step, resulting in a qualitatively changed angular dependence of the coercive fields. Similar experiments have been performed for nano-squares with walls of rectangular cross-section. This study allows for estimation of the reliability of magnetic properties of nano-structures with respect to undesired shape modifications in the lithography process.


T. Blachowicz and A. Ehrmann
Magnetization reversal in 3D nano-structures of different shapes
AIP Conf. Proc. 1727, 020003 (2016)

Abstract: Magnetic nano-particles have been intensively studied during the last decade due to their potential utilization in various applications. An important topic is the dependence of magnetic properties on the exact samples shape. After demonstrating the influence of shape distortions in magnetic nano half-spheres on magnetization reversal processes and hysteresis shapes, a series of different 3D nano-objects from permalloy with shape modifications has been examined with respect to their magnetic properties. Modifications are performed by cutting parts of diverse samples between the extrema of a cuboid and a half-sphere. Simulations of these samples have been performed by Magpar, using external magnetic fields along two different axes, swept with two different speeds. Depending on the original particle shape and its modifications, several phenomena can be found: Cutting a hole in a cuboid can switch the hard axis from out-of-plane to the in-plane direction. In some nano-particles, strong oscillations occur which can be suppressed by appropriate shape modifications. In some of the nano-objects, the magnetization reversal mechanism is completely altered by a change in the field sweeping speed. The article gives an overview of the different possibilities to tailor magnetic properties of nano-systems.


A. Ehrmann, S. Komraus, T. Blachowicz, K. Domino, M.-K. Nees, P.-J. Jakobs, H. Leiste, M. Mathes, and M. Schaarschmidt
Pseudo exchange bias due to rotational anisotropy
J. Magn. Magn. Mat. 412, 7-10 (2016)

Abstract: Ferromagnetic nanostructure arrays with particle dimensions between 160 nm and 400 nm were created by electron-beam lithography. The permalloy structures consist of rectangular-shaped walls around a square open space. While measuring their magnetic properties using the Magneto-Optical Kerr Effect (MOKE), in some angular regions an exchange bias (EB) seemed to appear. This paper gives an overview of possible reasons for this “pseudo exchange bias” and shows experimentally and by means of micromagnetic simulations that this effect can be attributed to unintentionally measuring minor loops.


A. Popowicz, T. Blachowicz
A simple multipurpose double-beam optical image analyzer
Rev. Sci. Instr. 87, 073105 (2016)

Abstract: In the paper we present a low cost optical device which splits the light in the focal plane into two separate optical paths and collimates it back into a single image plane, and where a selective information processing can be carried out. The optical system is straightforward and easily implementable as it consists of only three lenses and two mirrors. The system is dedicated for imaging in low-light-level conditions in which widely used optical devices, based on beam splitters or dichroic mirrors, suffer from light loss. We expose examples of applications of our device, using a prototype model. The proposed optical system may be employed for: monitoring the objects located at different distances from observer (1), creating regions of different magnification within a single image plane (2), high dynamic range photometry (3), or imaging in two wavelength bands simultaneously (4).


T. Blachowicz, A. Ehrmann, K. Domino
Statistical analysis of digital images of periodic fibrous structures using generalized Hurst exponent distributions
Physica A: Statistical Mechanics and its Applications 452, 167-177 (2016)

Abstract: Distinction of diverse two-dimensional periodic structures can be based on a large number of methods and parameters, while the quantitative description of differences between similar samples is usually difficult. This article aims, by the use of statistical random walk in a generalized q-order dimensional space, at introducing a methodology to qualify the networked structures on the base of exemplary textile samples. The presented results were obtained at 1-bit monochromatic maps obtained from optical microscopic pictures. Significant features of samples were represented by the obtained distributions of Hurst exponents and Shannon entropy calculations.


M. O. Weber, S. Aumann, M. Obermann, A. Ehrmann
Renewable Materials for Stab Resistance
in: F. Fangueiro, S. Rana (Eds.): Natural Fibres: Advances in Science and Technology Towards Industrial Applications, RILEM Bookseries, Springer International Publishing, 363-370 (2016)

Abstract: Different materials were investigated experimentally with respect to their stab resistance. The focus of this research is the use of renewable cellulosic materials , such as cotton and paper, in comparison with high-performance materials, such as aramid or ultra-high-molecular-weight polyethylene. The tests were carried out according to the standard of the Association of Test Laboratories for Bullet, Stab or Pike Resistant Materials and Construction Standards (VPAM). The results for common cellulosic materials achieve remarkable results in comparison with high-performance materials. Depending on the stab resistance being compared in terms of fabric thickness or mass per unit area, especially standard paper performed well, while even common cotton depicted a significant stab resistance . The results of these investigations demonstrate the advantages and limitations of renewable cellulosic materials in comparison to high-performance fibrous structures.



2015

A. Ehrmann, T. Blachowicz, K. Domino, S. Aumann, M. O. Weber, H. Zghidi
Examination of hairiness changes due to washing in knitted fabrics using a random walk approach (Abstract)
Text. Res. J. 85, 2147-2154 (2015)

Abstract: The relaxation of knitted fabrics is usually described in terms of dimensional changes of knitted loop widths and heights or fabric widths and heights, respectively. Due to washing, however, additional changes in the optical appearance and the haptic properties of a knitted fabric can occur, such as a change in the regularity or the hairiness. This article uses the random walk statistical approach to estimate the structural complexity of knitted fabrics directly after production and up to 10 washing cycles and shows that the Hurst exponent, resulting from the random walk process, is partly related to the cover factor of the knitted fabrics under investigation; however, it depicts significant contributions of the hairiness. Thus, this novel approach offers a quantitative measure of structural changes in knitted fabrics that cannot be described by cover factor or dimensional changes.


H. Zghidi, M. Walczak, T. Blachowicz, K. Domino, A. Ehrmann
Image Processing and Analysis of Textile Fibers by Virtual Random Walk
Proceedings of the 2015 Federated Conference on Computer Science and Information Systems, Annals of Computer Science and Information Systems 5, 717-720 (2015)

Abstract: An algorithm for extracting material shape and spatial information from non-uniform background, and for generating object skeletons for statistical two-dimensional experiments using random walk approach, is presented. This finds applications in textile analysis and microscopic analysis of various materials like hairs and allows for further precise determination of textile yarn dimensions as well as other geometrical characteristics like a fractal dimension.


A. Ehrmann, T. Blachowicz, H. Zghidi, M. O. Weber
Reliability of statistic evaluation of microscopic pictures taken from knitted fabrics
Journal of Physics: Conference Series 633, 012101 (2015)

Abstract: One of the techniques which can be used to quantitatively evaluate images statistically is the so-called random-walk approach. The resulting Hurst exponent is a measure of the complexity of the picture. Especially long, fine elements in the image, such as fibres, influence the Hurst exponent significantly. Thus, determination of the Hurst exponent has been suggested as new method to measure the hairiness of yarns or knitted fabrics, since existing hairiness measurement instruments are based on different measurement principles which are not comparable. While the principal usability of this method for hairiness detection has been shown in former projects, the absolute value of the calculated Hurst exponents depends on the technique to take the photographic image of a sample, to transfer it into a monochrome picture, and on possible image processing steps. This article gives an overview of edge detection filters, possible definitions of the threshold value between black and white for the transformation into a monochrome image, etc. It shows how these parameters should be chosen in case of typical textile samples and correlates the challenges of this novel method with well-known problems of common techniques to measure yarn and fabric hairiness.


T. Blachowicz, A. Ehrmann
Magnetization reversal modes in fourfold Co nano-wire systems
Journal of Physics: Conference Series 633, 012100 (2015)

Abstract: Magnetic nano-wire systems are, as well as other patterned magnetic structures, of special interest for novel applications, such as magnetic storage media. In these systems, the coupling between neighbouring magnetic units is most important for the magnetization reversal process of the complete system, leading to a variety of magnetization reversal mechanisms. This article examines the influence of the magnetic material on hysteresis loop shape, coercive field, and magnetization reversal modes. While iron nano-wire systems exhibit flat or one-step hysteresis loops, systems consisting of cobalt nano-wires show hysteresis loops with several longitudinal steps and transverse peaks, correlated to a rich spectrum of magnetization reversal mechanisms. We show that changing the material parameters while the system geometry stays identical can lead to completely different hysteresis loops and reversal modes. Thus, especially for finding magnetic nano-systems which can be used as quaternary or even higher-order storage devices, it is rational to test several materials for the planned systems. Apparently, new materials may lead to novel and unexpected behaviour – and can thus result in novel functionalities.


C. Richter, S. Schmülling, A. Ehrmann, K. Finsterbusch
FDM printing of 3D forms with embedded fibrous materials
Design, Manufacturing and Mechatronics, pp. 961-969 (2015)

Abstract: In the process of 3D printing, a three-dimensional form is created by additive manufacturing. The data provided by a 3D model are converted into a real object which is printed layer by layer. 3D printing is of particular interest for the production of small parts in small numbers, i.e. individualized items. Especially in the textile and clothing industry, 3D printing accessories, extensions etc. can be used to modify design as well as function of a base object which is created by typical textile production processes, such as weaving, knitting or sewing. Combining 3D printed objects with textile or fibrous materials, however, often results in low adhesion forces between both parts and therefore delamination of layers of different materials. The article thus describes efforts to create bi-material 3D printed objects and to enhance the bonding properties between contacting parts from different materials.


A. Ehrmann, T. Blachowicz
Influence of shape and dimension on magnetic anisotropies and magnetization reversal of Py, Fe, and Co nano-objects with four-fold symmetry
AIP Advances 5, 097109 (2015)

Abstract: Different magnetic anisotropies and magnetization reversal mechanisms were identified in magnetic nano-objects of four-fold symmetry, using micromagnetic simulations. Nano-particles with lateral dimensions between 50 nm and 400 nm, simulated with typical properties of permalloy, iron and cobalt, were tested in dependence of the angular orientation with respect to the externally applied magnetic field. All nano-objects exhibited steps on the sides of the hysteresis loops, which can be correlated with stable intermediate states at remanence, for some angular regions. Coercive fields were found to show an irregular and unpredictable angular dependence in case of cobalt nano-particles, while this material depicted the largest number of steps in general. Comparing the angular dependence of the coercive fields with previous calculations, it was shown that usual descriptions of fourfold anisotropies are no longer valid in most of the nano-objects under examination.


T. Blachowicz, K. Cwikiel, M. Binkowski, H. Zghidi
Analysis of the three-dimensional TGS crystal spatial inhomogeneity of fractal structure
Chaos Solitons & Fractals 75, 185-190 (2015)

Abstract: The new analysis of fractal spatial inhomogeneity of the fractal structure imitating evolution of fractal dimension during three-dimensional TGS crystal growth is provided. A final crystal structure was scanned layer-by-layer using X-ray tomography. Two-dimensional images were gradually imposed in order to calculate capacity fractal dimension. The spatio-temporal aspects of crystal growth were revealed by wavelet analysis and the main growth phases were determined.


L. Sabantina, F. Kinzel, A. Ehrmann, K. Finsterbusch
Combining 3D printed forms with textile structures - mechanical and geometrical properties of multi-material systems
IOP Conf. Series: Materials Science and Engineering 87, 012005 (2015)

Abstract: The 3D printing belongs to the rapidly emerging technologies which have the chance to revolutionize the way products are created. In the textile industry, several designers have already presented creations of shoes, dresses or other garments which could not be produced with common techniques. 3D printing, however, is still far away from being a usual process in textile and clothing production. The main challenge results from the insufficient mechanical properties, especially the low tensile strength, of pure 3D printed products, prohibiting them from replacing common technologies such as weaving or knitting. Thus, one way to the application of 3D printed forms in garments is combining them with textile fabrics, the latter ensuring the necessary tensile strength. This article reports about different approaches to combine 3D printed polymers with different textile materials and fabrics, showing chances and limits of this technique.


A. Ehrmann, T. Blachowicz, S. Komraus, M.-K. Nees, P.-J. Jakobs, H. Leiste, M. Mathes, and M. Schaarschmidt
Magnetic properties of square Py nanowires: irradiation dose and geometry dependence
Journal of Applied Physics 117, 173903 (2015)

Abstract: Arrays of ferromagnetic patterned nanostructures with single particle lateral dimensions between 160 nm and 400 nm were created by electron-beam lithography. The fourfold particles with rectangular-shaped walls around a square open area were produced from permalloy. Their magnetic properties were measured using the longitudinal magneto-optical Kerr effect. The article reports about the angle-dependent coercive fields and the influence of the e-beam radiation dose on sample shapes. It is shown that a broad range of radiation dose intensities enables reliable creation of nanostructures with parameters relevant for the desired magnetization reversal scenario. The experimental results are finally compared with micromagnetic simulations to explain the findings.


A. Ehrmann, T. Błachowicz, K. Domino, S. Aumann, M. O. Weber, and H. Zghidi
Examination of hairiness changes due to washing in knitted fabrics using a random walk approach
Text. Res. J., online first (2015)

Abstract: The relaxation of knitted fabrics is usually described in terms of dimensional changes of knitted loop widths and heights or fabric widths and heights, respectively. Due to washing, however, additional changes in the optical appearance and the haptic properties of a knitted fabric can occur, such as a change in the regularity or the hairiness. This article uses the random walk statistical approach to estimate the structural complexity of knitted fabrics directly after production and up to 10 washing cycles and shows that the Hurst exponent, resulting from the random walk process, is partly related to the cover factor of the knitted fabrics under investigation; however, it depicts significant contributions of the hairiness. Thus, this novel approach offers a quantitative measure of structural changes in knitted fabrics that cannot be described by cover factor or dimensional changes.


A. Ehrmann, T. Blachowicz and H. Zghidi
Spreadsheet analysis of stability and meta-stability of low-dimensional magnetic particles using the Ising approach
Eur. J. Phys. 36, 035028 (2015)

Abstract: Modelling hysteresis behaviour, as it can be found in a broad variety of dynamical systems, can be performed in different ways. An elementary approach, applied for a set of elementary cells, which uses only two possible states per cell, is the Ising model. While such Ising models allow for a simulation of many systems with sufficient accuracy, they nevertheless depict some typical features which must be taken into account with proper care, such as meta-stability or the externally applied field sweeping speed. This paper gives a general overview of recent results from Ising models from the perspective of a didactic model, based on a 2D spreadsheet analysis, which can be used also for solving general scientific problems where direct next-neighbour interactions take place.


K. Domino, T. Blachowicz
The use of copula functions for modeling the risk of investment in shares traded on world stock exchanges
Physica A 424, 142-151 (2015)

Abstract: In this paper the two dimensional model of the investment in shares is presented. The shares prices from five different world stock exchanges (New York, London, Frankfurt, Honk Kong, and Sydney) are examined. The copula functions are used to model the risk of investment. The Hurst threshold exponent derived from the local Detrended Fluctuation Analysis is used to determine the safe investment portfolios with no extreme drops in shares prices. The most important result states that the threshold value is not universal for different markets, however, it is influenced by the subsequent level of market freedom. It was shown, that the level, relatively larger in US, UK, and Australia than in Germany and China, affects the Hurst exponent threshold value.


M. Türk, A. Ehrmann & B. Mahltig
Water-, oil-, and soil-repellent treatment of textiles, artificial leather, and leather
Journal of the Textile Institute 106, 611-620 (2015)

Abstract: Several products are on the market to realize water-, oil-, and soil-repellent properties on textiles or textile-related materials. To make an adequate and fast rating of repellent properties of finished textiles, different drop tests according to AATCC and ISO standards are commonly used. For evaluation of the repellent properties of solid substrates against different liquids often contact angle measurements are performed. The aim of the work presented here is to determine and evaluate the repellent effects gained by the application of three different finishing agents on three different substrates, such as polyester fabric, artificial leather, and leather. The main questions are at that point: It is possible to gain similar repellent effects with the same finishing product applied on different substrates? Do the different testing methods lead to comparable results? Is there a relation to the repellency against everyday consumer products as red wine, ice tea, or coffee? This article should help the reader to evaluate different testing methods and the influence on common substrates.


T. Blachowicz, K. Cwikiel, M. Binkowski, H. Zghidi
Analysis of the three-dimensional TGS crystal spatial inhomogeneity of the fractal structure
Chaos, Solitons & Fractals 75, 185-190 (2015)

Abstract: The new analysis of fractal spatial inhomogeneity of the fractal structure imitating evolution of fractal dimension during three-dimensional TGS crystal growth is provided. A final crystal structure was scanned layer-by-layer using X-ray tomography. Two-dimensional images were gradually imposed in order to calculate capacity fractal dimension. The spatio-temporal aspects of crystal growth were revealed by wavelet analysis and the main growth phases were determined.


T. Blachowicz, Krzysztof Domino
The use of copula functions for modeling the risk of investment in shares traded on world stock exchanges
Physica A: Statistical Mechanics and its Applications 424, 142-151 (2015)

Abstract: In this paper the two dimensional model of the investment in shares is presented. The shares prices from five different world stock exchanges (New York, London, Frankfurt, Honk Kong, and Sydney) are examined. The copula functions are used to model the risk of investment. The Hurst threshold exponent derived from the local Detrended Fluctuation Analysis is used to determine the safe investment portfolios with no extreme drops in shares prices. The most important result states that the threshold value is not universal for different markets, however, it is influenced by the subsequent level of market freedom. It was shown, that the level, relatively larger in US, UK, and Australia than in Germany and China, affects the Hurst exponent threshold value.


A. Ehrmann, T. Blachowicz
A simple model of hysteresis behavior using spreadsheet analysis
Journal of Physics: Conference Series 574, 012158 (2015)

Abstract: Hysteresis loops occur in many scientific and technical problems, especially as field dependent magnetization of ferromagnetic materials, but also as stress-strain-curves of materials measured by tensile tests including thermal effects, liquid-solid phase transitions, in cell biology or economics. While several mathematical models exist which aim to calculate hysteresis energies and other parameters, here we offer a simple model for a general hysteretic system, showing different hysteresis loops depending on the defined parameters. The calculation which is based on basic spreadsheet analysis plus an easy macro code can be used by students to understand how these systems work and how the parameters influence the reactions of the system on an external field. Importantly, in the step-by-step mode, each change of the system state, compared to the last step, becomes visible. The simple program can be developed further by several changes and additions, enabling the building of a tool which is capable of answering real physical questions in the broad field of magnetism as well as in other scientific areas, in which similar hysteresis loops occur.


T. Blachowicz, A. Ehrmann
Anatomy of Demagnetizing and Exchange Fields in Magnetic Nano-Dots Influenced by 3D Shape Modifications
Journal of Physics: Conference Series 574, 012054 (2015)

Abstract: Hysteresis loops of 3D ferromagnetic permalloy nano-half-balls (dots) with 100 nm base diameter have been examined by means of LLG micromagnetic simulations and finite element methods. Tests were carried out with two orthogonal directions of the externally applied field at 10 kA/(m.ns) field sweeping speed. The comparison of samples with different 3D modifications at the sub-10nm scale, accessible by nowadays lithographic techniques, enables conclusions about different mechanisms of competition between demagnetizing and exchange fields. Design paradigms provided here can be applied, e.g., in bit-patterned media used as novel magnetic storage systems.


A. Ehrmann, T. Blachowicz
Micromagnetic simulation of fibers and coatings on textiles
Journal of The Institution of Engineers (India): Series E, online first

Abstract: Simulations of mechanical or comfort properties of fibers, yarns and textile fabrics have been developed for a long time. In the course of increasing interest in smart textiles, models for conductive fabrics have also been developed. The magnetic properties of fibers or magnetic coatings, however, are almost exclusively being examined experimentally. This article thus describes different possibilities of micromagnetically modeling magnetic fibers or coatings. It gives an overview of calculation times for different dimensions of magnetic materials, indicating the limits due to available computer performance and shows the influence of these dimensions on the simulated magnetic properties for magnetic coatings on fibers and fabrics.



2014

A. Ehrmann, T. Blachowicz, F. Heimlich, A. Brücken, M. O. Weber
Influence of the sample dimension and yarn type on the washing relaxation process of knitted fabrics
Tekstil 63, 163-167 (2014)

Abstract: While tailoring a garment or a technical textile, relaxation processes of a knitted fabric after production have to be taken into account. Such dimensional changes can occur during a long time of dry relaxation, during wet relaxation, or during washing relaxation, the latter having the strongest influence on a fabric. Besides fabric construction and yarn material, the dimensions of a knitted fabric also strongly influence the relaxation process. Our paper shows a detailed analysis of the first 50 washing cycles for different fabric dimensions and yarn parameters, comparing conventional yarns and a conductive yarn used in sensory technologies. Stitch widths in different locations in fabric samples were considered for analyzing the relaxation behavior.


A. Ehrmann, F. Heimlich, A. Brücken, M. O. Weber, R. Haug
Suitability of knitted fabrics as elongation sensors subject to structure, stitch dimension and elongation direction
Textile Research Journal 84, 2006-2012 (2014)

Abstract: The area of smart textiles has recently attracted more and more attention. One of the challenges in this domain is the development of textile sensors, such as textile electrodes, pressure sensors, elongation sensors, etc., mostly containing conductive yarn and/or conductive coating. One possibility to build a textile elongation sensor which can, for example, be utilized as a breathing sensor in a smart shirt, is using knitted fabrics created from conductive yarns, which often show a strong dependence of the electric resistance on the elongation. Due to the typical wearing out of knitted fabrics, however, the time-dependent behavior of a stretched fabric must also be taken into account. The article thus shows the results of elongation-dependent and time-dependent resistance measurements on knitted fabrics, produced from different yarns in various structures and stitch dimensions, elongated in different orientations with respect to the course direction. The results of our study show that full cardigan with medium stitch size is better suited for use as an elongation sensor than double face fabrics or other stitch sizes. These findings are not influenced by the stainless steel fraction in the conduction yarn, while mixing this yarn with a non-conductive one causes undesired signal deviations.


A. Ehrmann
Examination and simulation of new magnetic materials for the possible application in memory cells
ISBN 978-3-8325-3772-2, Logos Verlag, Berlin 2014

Abstract: Magnetic storage media are a topic of great interest for technological and fundamental research.
Examinations of nanostructured magnetic systems for storage media often aim at decreasing the pattern size, in order to enhance the possible information density in a given area. Here another approach is chosen: Intermediate magnetic states, occurring during magnetization reversal, which are stable at zero external field, can lead to quaternary or higher-order multilevel magnetic storage media. In this way, the storage density can be enhanced without decreasing the size of the magnetic nanoparticles.
The book describes different nanostructured systems in which such additional stable states can be found in simulation and experiment, examines their magnetization reversal dynamics, and gives recommendations for shapes and materials of future nanostructured systems for data storage media.


A. Ehrmann and T. Blachowicz
Influence of fourfold anisotropy form on hysteresis loop shape in ferromagnetic nanostructures
AIP Advances 4, 087115 (2014)

Abstract: The dependence of the form of different mathematical depictions of fourfold magnetic anisotropies has been examined, using a simple macro-spin model. Strong differences in longitudinal and transverse hysteresis loops occur due to deviations from the usual phenomenological model, such as using absolute value functions. The proposed possible models can help understanding measurements on sophisticated magnetic nanosystems, like exchange bias layered structures employed in magnetic hard disk heads or magnetic nano-particles, and support the development of solutions with specific magnetization reversal behavior needed in novel magneto-electronic devices.


K. Domino, T. Blachowicz, M. Ciupak
The use of copula functions for predictive analysis of correlations between extreme storm tides
Physica A: Statistical Mechanics and its Applications 413, 489-497 (2014)

Abstract: In this paper we present a method used in quantitative description of weakly predictable hydrological, extreme events at inland sea. Investigations for correlations between variations of individual measuring points, employing combined statistical methods, were carried out. As a main tool for this analysis we used a two-dimensional copula function sensitive for correlated extreme effects. Additionally, a new proposed methodology, based on Detrended Fluctuations Analysis (DFA) and Anomalous Diffusion (AD), was used for the prediction of negative and positive auto-correlations and associated optimum choice of copula functions. As a practical example we analysed maximum storm tides data recorded at five spatially separated places at the Baltic Sea. For the analysis we used Gumbel, Clayton, and Frank copula functions and introduced the reversed Clayton copula. The application of our research model is associated with modelling the risk of high storm tides and possible storm flooding.


R. Melnikova, A. Ehrmann, K. Finsterbusch
3D printing of textile-based structures by Fused Deposition Modelling (FDM) with different polymer materials
IOP Conf. Ser.: Mater. Sci. Eng. 62, 012018 (2014)

Abstract: 3D printing is a form of additive manufacturing, i.e. creating objects by sequential layering, for pre-production or production. After creating a 3D model with a CAD program, a printable file is used to create a layer design which is printed afterwards. While often more expensive than traditional techniques like injection moulding, 3D printing can significantly enhance production times of small parts produced in small numbers, additionally allowing for large flexibility and the possibility to create parts that would be impossible to produce with conventional techniques. The Fused Deposition Modelling technique uses a plastic filament which is pushed through a heated extrusion nozzle melting the material. Depending on the material, different challenges occur in the production process, and the produced part shows different mechanical properties. The article describes some standard and novel materials and their influence on the resulting parts.


W. Andreychouk, T. Błachowicz, K. Domino
Fractal dimensions of gypsum cave-mazes of Western Ukraine
Speleology and Karstology 11, 40-47 (2013)

Abstract: Gypsum maze caves of Western Ukraine are characterized by a complex spatial structure, which can be treated as fractals and can be studied using appropriate mathematical tools. Capacitance and correlation fractal dimensions of largest gypsum caves of the region were calculated. The results were used to predict findings of new, yet undiscovered parts of cave mazes.


S. Aumann, S. Trummer, A. Brücken, A. Ehrmann, A. Büsgen
Conceptual design of a sensory shirt for fire-fighters (Abstract / pdf)
Textile Research Journal 84, 1661-1665 (2014)

Abstract: A large number of fatal accidents of fire-fighters during operations can be attributed to circulatory collapses due to cardiovascular diseases or heat stress. A recent project thus aimed at developing a highly functional, reliable and suitable system which can be used under different conditions such as common indoor operations. Measurement of vital signs, like ECG, breathing, and skin temperature, had to be combined with limited weight, acceptable skin comfort, affordable price, and speed and ease of dress and connection to the electronics in the fire-fighter’s jacket. The article gives an overview of technical and clothing technology aspects of the developed sensory shirt.



2013

T. Blachowicz and A. Ehrmann
Micromagnetic simulations of anisotropies in coupled and uncoupled ferromagnetic nano-wire systems
Sci World J 2013, 472597 (2013)

Abstract: The influence of a variation of spatial relative orientations onto the coupling dynamics and subsequent magnetic anisotropies was modeled in ferromagnetic nanowires. The wires were analyzed in the most elementary configurations, thus, arranged in pairs perpendicular to each other, leading to one-dimensional (linear) and zero-dimensional (point-like) coupling. Different distances within each elementary pair of wires and between the pairs give rise to varying interactions between parallel and perpendicular wires, respectively. Simulated coercivities show an exchange of easy and hard axes for systems with different couplings. Additionally, two of the systems exhibit a unique switching behavior which can be utilized for developing new functionalities.


W. Andreychouk, T. Błachowicz, K. Domino
Fractal dimensions of cave for exemplary gypsum cave-mazes of Western Ukraine
Landform Analysis 22, 3-8 (2013)

Abstract: Gypsum labyrinthine caves are characterized by a complex spatial structure, which can be treated as fractals and can be studied using appropriate mathematical tools. Capacitance and correlation fractal dimensions of largest gypsum caves of the Western Ukraine (as well as the World’s largest ones) were calculated. The results were used to predict findings of new, undiscovered cave mazes parts.


M. O. Weber, F. Akter, A. Ehrmann
Shielding of static magnetic fields by textiles
Industria Textila 64, 184-187(2013)

Abstract: Low-frequency and static magnetic fields occur, e.g., in mains transformers, motors, oscilloscopes, strong laboratory magnets etc. They can be shielded only by materials of high permeability. For weak magnetic fields, μ-metal or Metglas have very high permeabilities leading to large shielding factors. However, both materials are not suited for larger fields, since the field-dependent permeability decreases significantly for magnetic fields of about 1 Oersted (Oe) or higher. In our experiments, we integrated metallic fine yarns fine and yarns from different magnetic materials into warp-knitted fabrics. These fabrics were formed into cylinders of defined diameter. The shielding factor was measured in the field range of ± 100 Oe. Shielding ratios were found to be much lower than values of a solid steel bar; however, these experiments point out that shielding of static magnetic fields with magnetic textiles is possible in principle.


T. Blachowicz, A. Ehrmann, P. Steblinski, J. Palka
Directional-dependent coercivities and magnetization reversal mechanisms in fourfold ferromagnetic systems of varying sizes (Abstract / pdf)
J. Appl. Phys. 113, 013901 (2013)
Copyright (2013) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

Abstract: Different types of reversal processes, including either uniform-rotation or domain-wall driven processes, were indentified in magnetic nano-wires of four-fold symmetry using micromagnetic simulations. Iron wires were tested for diameters ranging from 6 nm up to 20 nm, while their lengths were taken from 30 nm to 70 nm range, and for several directions of externally applied magnetic field. Physical parameters of presented low-dimensional structures enabled reversal via intermediate states, which can lead to additional stable states at remanence, contrary to instable vortexes observed in magnetic nano-rings or cylindrical nanodots.


T. Blachowicz, A. Ehrmann
Six-state, three-level, six-fold ferromagnetic wire system (Abstract / pdf)
J. Magn. Magn. Mat. 331, 21-23 (2013)
NOTICE: this is the author’s version of a work that was accepted for publication in <J. Magn. Magn. Mater.>. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in J. Magn. Magn. Mater. 331, 21-23 (2013), http://dx.doi.org/10.1016/j.jmmm.2012.11.014

Abstract: Different types of reversal processes, including either uniform-rotation or domain-wall driven processes, were indentified in magnetic nano-wires of four-fold symmetry using micromagnetic simulations. Iron wires were tested for diameters ranging from 6 nm up to 20 nm, while their lengths were taken from 30 nm to 70 nm range, and for several directions of externally applied magnetic field. Physical parameters of presented low-dimensional structures enabled reversal via intermediate states, which can lead to additional stable states at remanence, contrary to instable vortexes observed in magnetic nano-rings or cylindrical nanodots.