Pulsed-field studies of the magnetization reversal in molecular nanomagnets

We report experimental studies of crystals of Mn12 molecular magnetic clusters in pulsed magnetic fields with sweep rates up to 410^3 T/s . The steps in the magnetization curve are observed at fields that are shifted with respect to the resonant field values. The shift systematically increases as the rate of the field sweep goes up. These data are consistent with the theory of the collective dipolar relaxation in molecular magnets.

Properties of Anisotropic Superconductors in SR Model

The present thesis deals with the theoretical investigations on the effect of anisotropy on various properties of magnetically doped superconductors described by fihiba — Rusinov model.Chapter 1 is introductory. It contains a brief account of the current status of theory of superconductivity. In’ chapter 2 we give the formulation of the problem. Chapter 2.1 gives the BCS theory. The effect of magnetic impurities in superconductors as described by A8 theory is given in chapter 2.2A and that described by SR model is discussed in chapter 2.28. Chapter 2.2c deals with Kondo effect. In chapter 2.3 the anisotropy problem is reviewed. Our calculations, results and discussions are given in chapter 3. Chapter 3.1 deals with Josephson tunnel effect. In chapter 3.2 the thermodynamic critical field H62 is described. Chtpter 3.3 deals with the density of states. The ultrasonic attenuation coefficient and ufitlear spin relaxation are given in chapter 3.4 and 3.5 respectively. In chapter 3.6 we give the upper critical field calculations and chapter 3.7 deals with the response function. The Kondo effect is given in chapter 3.8. In chapter 4 we give the sumary of our results

”Studies on Selected conducting polymers for Microwave and Electrical Applications

The electrical properties of polymers make up an inherently interdisciplinary topic, being closely associated, on the one hand, with the mechanical properties of polymers polarization and relaxation) and, on the other hand, with the semi conductive properties (conduction and break down). In addition, unlike conventional technologies, which use these properties in its various applications like antistatic coatings, rechargeable batteries, sensors, electrochromic devices, electrochemical devices etc, microwave technology extract the microwave absorbing ability of electrically conducting polymers. The conducting polymers are widely used in its potential applications like electro magnetic interference shielding, satellite communication links, beam steering radars, frequency selective surfaces etc. Considering the relevance of microwave applications of conducting polymers, the study of microwave properties of conducting polymers stands poised to become a compelling choice for synthetic chemists and condensed - matter physicists, physical chemists and material scientists, electrochemists and polymer scientists. The main aim of the present work is to study the microwave and low frequency properties of various conducting polymers, conducting semi-interpenetrating networks, conducting copolymers and to characterise it. Also this thesis collated the microwave properties of these conducting systems and exposes the various technologically important applications in the industrial, scientific, communication and defence applications.

Electrical properties and phase transitions insome ammonium containing ferroelectrics

The thesis aims to present the results of the experimental investigations on the electrical properties like electrical conductivity, dielectric constant and ionic thermo~ currents in certain ammonium containing ferroelectric crystals viz. LiNH4SO4, (NH4)2SO4 and (NH4)5H(SO4)2. Special attention has been paid in revealing the mechanisms of electrical conduction in the various phases of these crystals and those asso~ ciated with the different phase transitions occurring in them, by making studies on doped, quenched and deuterated crystals. The report on the observation of two new phase transitions in (NH4) S O2 and of a similar one in ( NH4 ) H (2SO4 ) are included. The relaxation mechanisms of the impurity-vacancy complexes and the space charge phenomena in pure and doped crystals of LiNH4SO4 and (NH4)2SO4 and the observation of a new type of ionic thermo-current viz. Protonic Thermo-Current (PTC) in these crystals are also presented here.

“Studies on short polyester fiber - polyurethane elastomer composite with different interfacial bonding agents”

The work presented in this thesis is regarding the development and evaluation of new bonding agents for short polyester fiber - polyurethane elastomer composites. The conventional bonding system based on hexamethylenetetramine, resorcinol and hydrated silica was not effective as a bonding agent for the composite, as the water eliminated during the formation of the RF resin hydrolysed the urethane linkages. Four bonding agents based on MDI/'I‘DI and polypropyleneglycol, propyleneglycol and glycerol were prepared and the composite recipe was optimised with respect to the cure characteristics and mechanical properties. The flow properties, stress relaxation pattern and the thermal degradation characteristics of the composites containing different bonding agents were then studied in detail to evaluate the new bonding systems. The optimum loading of resin was 5 phr and the ratio of the -01 to isocyanate was 1:1. The cure characteristics showed that the optimum combination of cure rate and processability was given by the composite with the resin based on polypropyleneglycol/ glycerol/ 4,4’diphenylmethanediisocynate (PPG/GL/MDI). From the rheological studies of the composites with and without bonding agents it was observed that all the composites showed pseudoplastic nature and the activation energy of flow of the composite was not altered by the presence of bonding agents. Mechanical properties such as tensile strength, modulus, tear resistance and abrasion resistance were improved in the presence of bonding agents and the effect was more pronounced in the case of abrasion resistance. The composites based on MDI/GL showed better initial properties while composites with resins based on MDI/PPG showed better aging resistance. Stress relaxation showed a multistage relaxation behaviour for the composite. Within the-strain levels studied, the initial rate of relaxation was higher and the cross over time was lesser for the composite containing bonding agents. The bonding agent based on MDI/PPG/GL was found to be a better choice for improving stress relaxation characteristics with better interfacial bonding. Thennogravimetirc analysis showed that the presence of fiber and bonding agents improved the thennal stability of the polyurethane elastomer marginally and it was maximum in the case of MDI / GL based bonding agents. The kinetics of degradation was not altered by the presence of bonding agents

Evidence for polaron conduction in nanostructured manganese ferrite

Nanoparticles of manganese ferrite were prepared by the chemical co-precipitation technique. The dielectric parameters, namely, real and imaginary dielectric permittivity (ε and ε ), ac conductivity (σac) and dielectric loss tangent (tan δ), were measured in the frequency range of 100 kHz–8MHz at different temperatures. The variations of dielectric dispersion (ε ) and dielectric absorption (ε ) with frequency and temperature were also investigated. The variation of dielectric permittivity with frequency and temperature followed the Maxwell–Wagner model based on interfacial polarization in consonance with Koops phenomenological theory. The dielectric loss tangent and hence ε exhibited a relaxation at certain frequencies and at relatively higher temperatures. The dispersion of dielectric permittivity and broadening of the dielectric absorption suggest the possibility of a distribution of relaxation time and the existence of multiple equilibrium states in manganese ferrite. The activation energy estimated from the dielectric relaxation is found to be high and is characteristic of polaron conduction in the nanosized manganese ferrite. The ac conductivity followed a power law dependence σac = Bωn typical of charge transport assisted by a hopping or tunnelling process. The observed minimum in the temperature dependence of the frequency exponent n strongly suggests that tunnelling of the large polarons is the dominant transport process

Dielectric and Conductivity Studies on Cobalt Phthalocyanine Tetramers

Electrically conductive organic and metalloorganic polymers are of great interest and they have applications in electronic, optical, photonic, photoelectric, electrochemical, and dielectric devices. Tetrameric cobalt phthalocyanine was prepared by conventional chemical method. The dielectric permittivity of the tetrameric cobalt phthalocyanine sample was evaluated from the observed capacitance values in the frequency range 100 KHz to 5 MHz and in the temperature range of 300 to 383°K. It is found that the system obeys the Maxwell Wagner relaxation of space charge phenomenon. Further, from the permittivity studies AC conductivity was evaluated. The values of AC conductivity and DC conductivity were compared. Activation energy was calculated. To understand the conduction mechanism Mott’s variable range hopping model was applied to the system. The T 1/4 behavior of the DC conductivity along with the values of Mott’s Temperature (T0), density of states at the Fermi energy N (EF), and range of hopping R and hopping energy W indicate that the transport of charge carriers are by three-dimensional variable range hopping

On the dielectric dispersion and absorption in nanosized manganese zinc mixed ferrites

The temperature and frequency dependence of dielectric permittivity and dielectric loss of nanosized Mn1−xZnxFe2O4 (for x = 0, 0.2, 0.4, 0.6, 0.8, 1) were investigated. The impact of zinc substitution on the dielectric properties of the mixed ferrite is elucidated. Strong dielectric dispersion and broad relaxation were exhibited by Mn1−xZnxFe2O4. The variation of dielectric relaxation time with temperature suggests the involvement of multiple relaxation processes. Cole–Cole plots were employed as an effective tool for studying the observed phenomenon. The activation energies were calculated from relaxation peaks and Cole–Cole plots and found to be consistent with each other and indicative of a polaron conduction

Effect of nickel nanofillers on the dielectric and magnetic properties of composites based on rubber in the X-band

Nickel–rubber nanocomposites were synthesized by incorporating ferromagnetic nickel nanoparticles in a natural rubber as well as neoprene rubber matrix. Complex dielectric permittivity and magnetic permeability of these composites were evaluated in the X-band microwave frequencies at room temperature using cavity perturbation technique. The dielectric loss in natural rubber is smaller compared to neoprene rubber. A steady increase in the dielectric permittivity is observed with increase in the content of nickel in both the composites. The magnetic permeability exhibits a steady decrease with increase in frequency and magnetic loss shows a relaxation at 8 GHz. The suitability of these composites as microwave absorbers is modeled based on the reflection loss which is dependant on the real and imaginary components of the complex dielectric permittivity and magnetic permeability.

On the magnetic and dielectric properties of nickel–neoprene nanocomposites

Nickel nanocomposites were prepared by incorporating nickel nanoparticles in a neoprene matrix according to a specific recipe for various loadings of nickel particles. The dielectric properties of these composites were evaluated for different frequencies ranging from 100 kHz to 8MHz at different temperatures from 30 ◦C to 120 ◦C. The dielectric permittivity increases with increase of nickel concentration. Increase in temperature enhances the permittivity initially, till 40 ◦C and thereafter the permittivity decreases. The dielectric loss exhibits relaxation peaks and the peaks shift to lower frequencies with increase in volume fraction of the nickel nanoparticles in the matrix. The evaluation of magnetic and dielectric properties of these composites suggests that the dielectric permittivity can be tailored by an appropriate loading of the filler using semi-empirical equations and the magnetic properties vary according to simple mixture equations

Evidence for the existence of multiple equilibrium states in cobalt phthalocyanine tetramer: a study by dielectric spectroscopy

In any investigation, information about the molecules under consideration is very essential for tailoring their properties. Evaluation of dispersion parameters, namely optical dielectric constant, static dielectric constant, relaxation time and spreading factor, assumes significance in this context. Dielectric spectroscopy is a useful tool for estimating these parameters. Not only does it reveal details about these constants but it also gives insight into the mechanism of conduction. In this paper the evaluation of dispersion parameters of cobalt phthalocyanine tetramer in the temperature range 300–393K is attempted using Cole–Cole plots. The temperature variation of the spreading factor indicates the existence of multiple equilibrium positions in the case of cobalt phthalocyanine tetramer. To the best of our knowledge, the evaluation of dispersion parameters for cobalt phthalocyanine tetramer is reported for the first time

Magnetic and topographical modifications of amorphous Co–Fe thin films induced by high energy Ag7+ ion irradiation

We have investigated the effects of swift heavy ion irradiation on thermally evaporated 44 nm thick, amorphous Co77Fe23 thin films on silicon substrates using 100 MeV Ag7+ ions fluences of 1 1011 ions/ cm2, 1 1012 ions/cm2, 1 1013 ions/cm2, and 3 1013 ions/cm2. The structural modifications upon swift heavy irradiation were investigated using glancing angle X-ray diffraction. The surface morphological evolution of thin film with irradiation was studied using Atomic Force Microscopy. Power spectral density analysis was used to correlate the roughness variation with structural modifications investigated using X-ray diffraction. Magnetic measurements were carried out using vibrating sample magnetometry and the observed variation in coercivity of the irradiated films is explained on the basis of stress relaxation. Magnetic force microscopy images are subjected to analysis using the scanning probe image processor software. These results are in agreement with the results obtained using vibrating sample magnetometry. The magnetic and structural properties are correlated

Tailoring Magnetic Properties of Co-Fe Thin Films by Topographical Modifications Using Thermal Annealing and Swift Heavy Ion Irradiation and Fabrication of Magnetoelectric Multilayers for Device Applications

Magnetism and magnetic materials have been playing a lead role in improving the quality of life. They are increasingly being used in a wide variety of applications ranging from compasses to modern technological devices. Metallic glasses occupy an important position among magnetic materials. They assume importance both from a scientific and an application point of view since they represent an amorphous form of condensed matter with significant deviation from thermodynamic equilibrium. Metallic glasses having good soft magnetic properties are widely used in tape recorder heads, cores of high-power transformers and metallic shields. Superconducting metallic glasses are being used to produce high magnetic fields and magnetic levitation effect. Upon heat treatment, they undergo structural relaxation leading to subtle rearrangements of constituent atoms. This leads to densification of amorphous phase and subsequent nanocrystallisation. The short-range structural relaxation phenomenon gives rise to significant variations in physical, mechanical and magnetic properties. Magnetic amorphous alloys of Co-Fe exhibit excellent soft magnetic properties which make them promising candidates for applications as transformer cores, sensors, and actuators. With the advent of microminiaturization and nanotechnology, thin film forms of these alloys are sought after for soft under layers for perpendicular recording media. The thin film forms of these alloys can also be used for fabrication of magnetic micro electro mechanical systems (magnetic MEMS). In bulk, they are drawn in the form of ribbons, often by melt spinning. The main constituents of these alloys are Co, Fe, Ni, Si, Mo and B. Mo acts as the grain growth inhibitor and Si and B facilitate the amorphous nature in the alloy structure. The ferromagnetic phases such as Co-Fe and Fe-Ni in the alloy composition determine the soft magnetic properties. The grain correlation length, a measure of the grain size, often determines the soft magnetic properties of these alloys. Amorphous alloys could be restructured in to their nanocrystalline counterparts by different techniques. The structure of nanocrystalline material consists of nanosized ferromagnetic crystallites embedded in an amorphous matrix. When the amorphous phase is ferromagnetic, they facilitate exchange coupling between nanocrystallites. This exchange coupling results in the vanishing of magnetocrystalline anisotropy which improves the soft magnetic properties. From a fundamental perspective, exchange correlation length and grain size are the deciding factors that determine the magnetic properties of these nanocrystalline materials. In thin films, surfaces and interfaces predominantly decides the bulk property and hence tailoring the surface roughness and morphology of the film could result in modified magnetic properties. Surface modifications can be achieved by thermal annealing at various temperatures. Ion irradiation is an alternative tool to modify the surface/structural properties. The surface evolution of a thin film under swift heavy ion (SHI) irradiation is an outcome of different competing mechanism. It could be sputtering induced by SHI followed by surface roughening process and the material transport induced smoothening process. The impingement of ions with different fluence on the alloy is bound to produce systematic microstructural changes and this could effectively be used for tailoring magnetic parameters namely coercivity, saturation magnetization, magnetic permeability and remanence of these materials. Swift heavy ion irradiation is a novel and an ingenious tool for surface modification which eventually will lead to changes in the bulk as well as surface magnetic property. SHI has been widely used as a method for the creation of latent tracks in thin films. The bombardment of SHI modifies the surfaces or interfaces or creates defects, which induces strain in the film. These changes will have profound influence on the magnetic anisotropy and the magnetisation of the specimen. Thus inducing structural and morphological changes by thermal annealing and swift heavy ion irradiation, which in turn induce changes in the magnetic properties of these alloys, is one of the motivation of this study. Multiferroic and magneto-electrics is a class of functional materials with wide application potential and are of great interest to material scientists and engineers. Magnetoelectric materials combine both magnetic as well as ferroelectric properties in a single specimen. The dielectric properties of such materials can be controlled by the application of an external magnetic field and the magnetic properties by an electric field. Composites with magnetic and piezo/ferroelectric individual phases are found to have strong magnetoelectric (ME) response at room temperature and hence are preferred to single phasic multiferroic materials. Currently research in this class of materials is towards optimization of the ME coupling by tailoring the piezoelectric and magnetostrictive properties of the two individual components of ME composites. The magnetoelectric coupling constant (MECC) (_ ME) is the parameter that decides the extent of interdependence of magnetic and electric response of the composite structure. Extensive investigates have been carried out in bulk composites possessing on giant ME coupling. These materials are fabricated by either gluing the individual components to each other or mixing the magnetic material to a piezoelectric matrix. The most extensively investigated material combinations are Lead Zirconate Titanate (PZT) or Lead Magnesium Niobate-Lead Titanate (PMNPT) as the piezoelectric, and Terfenol-D as the magnetostrictive phase and the coupling is measured in different configurations like transverse, longitudinal and inplane longitudinal. Fabrication of a lead free multiferroic composite with a strong ME response is the need of the hour from a device application point of view. The multilayer structure is expected to be far superior to bulk composites in terms of ME coupling since the piezoelectric (PE) layer can easily be poled electrically to enhance the piezoelectricity and hence the ME effect. The giant magnetostriction reported in the Co-Fe thin films makes it an ideal candidate for the ferromagnetic component and BaTiO3 which is a well known ferroelectric material with improved piezoelectric properties as the ferroelectric component. The multilayer structure of BaTiO3- CoFe- BaTiO3 is an ideal system to understand the underlying fundamental physics behind the ME coupling mechanism. Giant magnetoelectric coupling coefficient is anticipated for these multilayer structures of BaTiO3-CoFe-BaTiO3. This makes it an ideal candidate for cantilever applications in magnetic MEMS/NEMS devices. SrTiO3 is an incipient ferroelectric material which is paraelectric up to 0K in its pure unstressed form. Recently few studies showed that ferroelectricity can be induced by application of stress or by chemical / isotopic substitution. The search for room temperature magnetoelectric coupling in SrTiO3-CoFe-SrTiO3 multilayer structures is of fundamental interest. Yet another motivation of the present work is to fabricate multilayer structures consisting of CoFe/ BaTiO3 and CoFe/ SrTiO3 for possible giant ME coupling coefficient (MECC) values. These are lead free and hence promising candidates for MEMS applications. The elucidation of mechanism for the giant MECC also will be the part of the objective of this investigation.

Spontane Strukturbildung in Mehrschichtsystemen unter Verwendung Molekularer Gläser

Den Schwerpunkt dieser Dissertation bildet zum einen die Entwicklung eines theoretischen Modells zur Beschreibung des Strukturbildungsprozesses in organisch/anorganischen Doppelschichtsystemen und zum anderen die Untersuchung der Übertragbarkeit dieser theoretisch gewonnenen Ergebnisse auf reale Systeme. Hierzu dienen systematische experimentelle Untersuchungen dieses Phänomens an einem Testsystem. Der Bereich der selbstorganisierenden Systeme ist von hohem wissenschaftlichen Interesse, erlaubt er doch die Realisierung von Strukturen, die nicht den Begrenzungen heutiger Techniken unterliegen, wie etwa der Beugung bei lithographischen Verfahren. Darüber hinaus liefert ein vertieftes Verständnis des Strukturbildungsprozesses auch eine Möglichkeit, im Falle entsprechender technischer Anwendungen Instabilitäten innerhalb der Schichtsysteme zu verhindern und somit einer Degradation der Bauteile entgegenzuwirken. Im theoretischen Teil der Arbeit konnte ein Modell im Rahmen der klassischen Elastizitätstheorie entwickelt werden, mit dessen Hilfe sich die Entstehung der Strukturen in Doppelschichtsystemen verstehen läßt. Der hier gefundene funktionale Zusammenhang zwischen der Periode der Strukturen und dem Verhältnis der Schichtdicken von organischer und anorganischer Schicht, wird durch die experimentellen Ergebnisse sehr gut bestätigt. Die Ergebnisse zeigen, daß es technologisch möglich ist, über die Vorgabe der Schichtdicke in einem Materialsystem die Periodizität der entstehenden Strukturen vorzugeben. Darüber hinaus liefert das vorgestellte Modell eine Stabilitätsbedingung für die Schichtsysteme, die es ermöglicht, zu jedem Zeitpunkt die dominierende Mode zu identifizieren. Ein Schwerpunkt der experimentellen Untersuchungen dieser Arbeit liegt auf der Strukturbildung innerhalb der Schichtsysteme. Das Testsystem wurde durch Aufbringen einer organischen Schicht - eines sog. Molekularen Glases - auf ein Glassubstrat realisiert, als Deckschicht diente eine Siliziumnitrid-Schicht. Es wurden Proben mit variierenden Schichtdicken kontrolliert erwärmt. Sobald die Temperatur des Schichtsystems in der Größenordnung der Glasübergangstemperatur des jeweiligen organischen Materials lag, fand spontan eine Strukturbildung auf Grund einer Spannungsrelaxation statt. Es ließen sich durch die Wahl einer entsprechenden Heizquelle unterschiedliche Strukturen realisieren. Bei Verwendung eines gepulsten Lasers, also einer kreisförmigen Wärmequelle, ordneten sich die Strukturen konzentrisch an, wohingegen sich ihre Ausrichtung bei Verwendung einer flächenhaften Heizplatte statistisch verteilte. Auffällig bei allen Strukturen war eine starke Modulation der Oberfläche. Ferner konnte in der Arbeit gezeigt werden, daß sich durch eine gezielte Veränderung der Spannungsverteilung innerhalb der Schichtsysteme die Ausrichtung der Strukturen (gezielt) manipulieren ließen. Unabhängig davon erlaubte die Variation der Schichtdicken die Realisierung von Strukturen mit einer Periodizität im Bereich von einigen µm bis hinunter zu etwa 200 nm. Die Kontrolle über die Ausrichtung und die Periodizität ist Grundvoraussetzung für eine zukünftige technologische Nutzung des Effektes zur kontrollierten Herstellung von Mikro- bzw. Nanostrukturen. Darüber hinaus konnte ein zunächst von der Strukturbildung unabhängiges Konzept eines aktiven Sensors für die optische Raster-Nahfeld-Mikroskopie vorgestellt werden, das das oben beschriebene System, bestehend aus einem fluoreszierenden Molekularen Glas und einer Siliziumnitrid-Deckschicht, verwendet. Erste theoretische und experimentelle Ergebnisse zeigen das technologische Potential dieses Sensortyps.

VUV-Laserablation von Spinnenseide

Spinnenseide gehört zu den stabilsten bekannten Polymerverbindungen. Spinnfäden können bis auf das Dreifache ihrer ursprünglichen Länge gedehnt werden, bevor sie reißen, und dabei mit rund 160 MJ/m³ mehr als dreimal soviel Energie absorbieren wie die stärkste synthetisch hergestellte Faser Kevlar (50 MJ/m³). Dabei weisen Spinnfäden mit 2 bis 5 Mikrometer nur ein Zehntel des Durchmessers eines menschlichen Haares auf. Das präzise, berührungslose Bearbeiten von Spinnenseide ist für verschiedene technische Anwendungen interessant, insbesondere wenn dabei ihre außergewöhnlichen Eigenschaften erhalten bleiben. Könnten die von Natur aus dünnen Seidenfäden gezielt in ihrem Durchmesser verringert werden, so wären sie unter anderem in der Mikroelektronik einzusetzen. Hier könnten sie als Trägermaterial für eine dünne, elektrisch leitfähige Schicht fungieren. Man erhielte Nanodrähte, die auch in mechanisch besonders belasteten Mikroelektronikbauteilen (MEMS) Verwendung finden könnten. In dieser Arbeit wird die Verwendung der laserinduzierten Ablation zur gezielten Bearbeitung von Haltefäden der Schwarzen Witwe (Latrodectus hesperus) beschrieben. Eingesetzt wurde ein VUV-Excimerlaser vom Typ LPF 205 (Lambda-Physik, Göttingen) mit einer Wellenlänge von 157 nm und einer Pulsdauer von 18 ns. Eine berührungslose Laserbearbeitung bei 157 nm erlaubt einen effizienten und präzisen Abtrag von Material durch Ablation aufgrund der geringen optischen Eindringtiefe von unter 100 nm oberhalb einer Schwellenfluenz (Energie/Fläche) von Φth=29 mJ/cm², ohne dabei das umgebende Material thermisch zu beeinträchtigen. Parallel zur Ablation setzt allerdings eine wellenförmige Oberflächenstrukturierung auf der Faseroberfläche ein, wodurch die mechanische Belastbarkeit der Faser entscheidend geschwächt wird. Die Ursache hierfür liegt im Abbau materialbedingter Spannungsfelder („stress release“) innerhalb einer durch das Laserlicht induzierten dünnen Schmelzschicht. Im Rahmen dieser Arbeit ist es nun gelungen, diese Strukturen durch einen anschließenden Glättungsprozeß zu entfernen. Dabei wird auf der bestrahlten Oberfläche mittels Laserlichts eine glatte Ablation erzielt. Mit feinerer Abstufung dieser Prozeßschritte konnte der Durchmesser des verwendeten Spinnenseidefadens zum Teil um 70 Prozent bis auf ca. 750 nm verringert werden. Durch Zugfestigkeitsexperimente wurde belegt, daß die mechanischen Eigenschaften der so bearbeiteten Spinnenseide weitgehend erhalten bleiben. Die im Rahmen dieser Arbeit angewandte Methode erlaubt somit eine präzise Laserablation von Spinnenseide und ähnlichen hochabsorbierenden Materialien, ohne deren Kernsubstanz in ihrer Beschaffenheit zu verändern.