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Tolke T.,Innovent Jena | Kriltz A.,Friedrich - Schiller University of Jena | Rechtenbach A.,Innovent Jena
Thin Solid Films | Year: 2010

TiO2-layers for self-cleaning applications were deposited on glass and silicon wafer by reactive dc-sputtering at various oxygen and argon pressures in the range from 0.18 Pa to 3.0 Pa. With an increasing sputtering pressure the microstructure of the resulting films is significantly modified. The deposited crystal phases change from rutile to anatase and the density and the refractive index decrease by a factor of about 1.3. The microstructure of the layers is strongly influenced by the sputtering pressure. An improvement of the hydrophilicity as well as of the photocatalytic activity can be observed, due to the changes in the structure of the layers. © 2010 Elsevier B.V. All rights reserved.

Michels A.,University of Luxembourg | Erokhin S.,Innovent Jena | Berkov D.,Innovent Jena | Gorn N.,Innovent Jena
Journal of Magnetism and Magnetic Materials | Year: 2014

The recent development of a micromagnetic simulation methodology - suitable for multiphase magnetic nanocomposites - permits the computation of the magnetic microstructure and of the associated magnetic small-angle neutron scattering (SANS) cross section of these materials. In this review we summarize results on the micromagnetic simulation of magnetic SANS from two-phase nanocomposites. The decisive advantage of this approach resides in the possibility to scrutinize the individual magnetization Fourier contributions to the total magnetic SANS cross section, rather than their sum, which is generally obtained from the experiment. The procedure furnishes unique and fundamental information regarding magnetic neutron scattering from nanomagnets. © 2013 Elsevier B.V.

Erokhin S.,Innovent Jena | Berkov D.,Innovent Jena | Gorn N.,Innovent Jena | Michels A.,University of Luxembourg
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We have used numerical micromagnetics for the calculation of the magnetic (small-angle) neutron scattering cross section dΣ M/dΩ of nanocomposites. In contrast to neutron experiments, in which one generally measures only a weighted sum of the Fourier components of the magnetization, our approach allows one to study the behavior of the individual contributions to dΣ M/dΩ. The procedure furnishes unique and fundamental information regarding the magnetic microstructure and corresponding magnetic scattering from nanomagnets. In particular, our simulations explain the recent observation of magnetodipolar correlations in two-phase nanocomposites and, moreover, suggest their relevance for a wide range of magnetic materials such as nanocomposites, nanoporous magnets, single-phase magnets with random anisotropy, and magnetic recording media. © 2012 American Physical Society.

Berkov D.V.,Innovent Jena | Boone C.T.,University of California at Irvine | Krivorotov I.N.,University of California at Irvine
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We present a detailed numerical analysis of the magnetization auto-oscillations induced in a thin NiFe nanowire by a direct spin-polarized current injected via a square-shaped CoFe nanomagnet. We demonstrate that all auto-oscillation modes in the nanowire are localized under the nanocontact for magnetic field applied in the plane of the nanowire. This mode localization is induced by a strong, stray magnetic field acting on the NiFe nanowire from the CoFe current injector. We find that the auto-oscillation frequency, power, and the frequency shift with the current strongly depend on the exchange constant of NiFe. We also find that the auto-oscillation power depends nonmonotonically on the CoFe saturation magnetization, and we demonstrate that this effect has its origin in resonant excitation of the CoFe eigenmodes by magnetization oscillations in the NiFe nanowire. The calculated dependence of the oscillation frequency on current is in good agreement with the experiment. However, the agreement between theory and experiment for the oscillation power is unsatisfactory. Finally, we have shown that an auto-oscillatory mode propagating along the nanowire in the system under study is possible when a sufficiently strong out-of-plane field is applied. © 2011 American Physical Society.

Schnabelrauch M.,Innovent Jena | Scharnweber D.,TU Dresden | Schiller J.,University of Leipzig
Current Medicinal Chemistry | Year: 2013

Glycosaminoglycans (GAG) such as hyaluronan (HA) or chondroitin/dermatan sulfate (CS/DS) occur in many connective tissues, for instance, in bone, cartilage and skin. Due to their significant water-binding capacity, GAG are essential for the biomechanical properties of these tissues. However, there is also increasing evidence that the sulfation of GAG does not occur at random, but a sulfation code exists that mediates the physiological functions of GAG. Thus, the biological properties of these biomacromolecules are strongly influenced by the degree of sulfation (ds) and the sulfate group distribution along the polymer. Therefore, certain GAG might also have interesting pharmacological properties. It is, thus, commonly accepted that GAG represent promising biomaterials in the field of tissue engineering as well as to design new bioactive materials for tissue repair and reconstruction. In this review we will focus on chemically sulfated GAG and provide a survey of these compounds on four different levels. First, we will provide an overview on chemical functionalization strategies of naturally occurring HA and CS/DS with special emphasis on regioselective methods to introduce a defined number of sulfate residues into the carbohydrate backbone. Second, chemical and biochemical methods to characterize the synthesized compounds will be introduced with the focus on methods based on nuclear magnetic resonance (NMR) and mass spectrometry (MS). In the third part, we will discuss the interaction of natural and chemically sulfated GAG with proteins and other biomolecules with regulatory functions. Additionally, biological consequences of these interactions regarding healing processes of skin and bone will be presented by discussing selected cell culture experiments. Finally, in vivo effects of GAG as components of artificial extracellular matrices will be discussed. © 2013 Bentham Science Publishers.

Semenova E.K.,Innovent Jena | Berkov D.V.,Innovent Jena
Journal of Applied Physics | Year: 2013

In this paper, we present a detailed numerical micromagnetic study of the spin wave propagation in a thin magnetic film where several columns of circular antidots (holes) are cut out. We determine the transmission coefficient of such a system as the function of the spin wave frequency (transmission spectrum), and study the absorption and transmission frequency regions in dependence on the interdot distances and on the number of antidot columns. It turns out that already several antidot columns are sufficient to obtain nearly perfect gaps in the transmission spectrum of spin waves, so that already a system of a few such columns can be used as a very effective magnonic filter. Next, we establish a close relation between the transmission spectrum of our system and the spectrum of eigenmodes of the corresponding infinite antidot lattice. Finally, we demonstrate that transmission and absorption bands can be easily tuned (for the given antidot arrangement) by changing the external magnetic field. Importantly, the transmission spectrum exhibits a universal scaling when the external field is changed, when this spectrum is plotted as the function of the magnon wave vector. © 2013 AIP Publishing LLC.

Erokhin S.,Innovent Jena | Berkov D.,Innovent Jena
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

Nonlinear magnetization dynamics in ferromagnetic nanoelements excited by a spin-polarized dc current is one of the most intensively studied phenomena in solid-state magnetism. Despite immense efforts, synchronization of oscillations induced in several such nanoelements [spin-torque-driven nano-oscillators (STNO)] still represents a major challenge from both the fundamental and technological points of view. In this paper we propose a system where synchronization of any number of STNOs, represented by magnetization vortices inside squared nanoelements, can be easily achieved. Using full-scale micromagnetic simulations we show that synchronization of these STNOs is extremely dynamically stable due to their very large coupling energy provided by the magnetodipolar interaction. Finally, we demonstrate that our concept allows robust synchronization of an arbitrary number of STNOs (arranged either as a one-dimensional chain or as a two-dimensional array), even when current supplying nanocontacts have a broad size distribution. © 2014 American Physical Society.

Berkov D.V.,Innovent Jena
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

In this paper we present numerical simulation studies of the synchronization of two coupled spin-torque nano-oscillators (STNO) in the quasi-one-dimensional (1D) geometry: magnetization oscillations are induced in a thin NiFe nanostripe by a spin-polarized current injected via square-shaped CoFe nanomagnets on the top of this stripe. In a sufficiently large out-of-plane field, a propagating oscillation mode appears in such a system. Due to the absence of the geometrically caused wave decay in 1D systems, this mode is expected to enable a long-distance synchronization between STNOs. Indeed, our simulations predict that synchronization of two STNOs on a nanowire is possible up to the intercontact distance ΔL=3μm (for the nanowire width w=50nm). However, we have also found several qualitatively important features of the synchronization behavior for this system, which make the achievement of a stable synchronization in this geometry a highly nontrivial task. In particular, there exists a minimal distance between the nanocontacts, below which a synchronization of STNOs cannot be achieved. Further, when the current value in the first contact is kept constant, the synchronized oscillation power depends nonmonotonously on the current value in the second contact. Finally, for one and the same current values through the contacts, there might exist several synchronized states (with different frequencies), depending on the initial conditions. © 2013 American Physical Society.

Schmidt J.,Innovent Jena
Metall | Year: 2013

Consideration of the results yielded leads to the conclusion that in principle an improvement in the corrosion protection by means of the coating of magnesium surfaces with atmospheric pressure plasma and subsequent powder painting is achievable. This improvement is considered to be the summation of pickling treatment and coating. The tests have shown that the specifically matched combination of phosphoric acid pickling treatment, the film coating with silicon oxide by means of atmospheric pressure plasma and a primer application with subsequent powder painting can provide efficient active corrosion protection layers which in terms of adhesion strength (fig. 7) and corrosion resistance (Table 1) can indeed compete with the chromating processes.

Struppert T.,Innovent Jena | Heft A.,Innovent Jena | Grunler B.,Innovent Jena
Thin Solid Films | Year: 2012

The use of the atmospheric pressure C-CVD (combustion chemical vapour deposition) process for the deposition of thin functional layers on float glass and plastics is described. We will give an overview on the variety of materials that can be deposited and some examples, like SiO 2, WO x and Ag, are presented in more detail with potential applications. © 2011 Elsevier B.V. All rights reserved.

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