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The ability to create atomically perfect, epitaxial heterostructures of correlated complex perovskite oxides using state-of-art thin film deposition techniques has generated new physical phenomena at engineered interfaces. Here we report on the impact of growth kinetics on the magnetic structure and exchange coupling at the interface in heterostructures combining layers of antiferromagnetic La

The thickness-driven spin-reorientation transition of Co/Au(1 1 1) is studied via in situ Kerr microscopy. On varying the premagnetization conditions in external field of in-plane or normal orientation, the magnetic switching into a final remanent state from an in-plane field is investigated. The quantitative analysis of the Kerr rotation derived from Kerr microscopy images allows the determination of the population of different magnetic phases as a function of thickness. Coexisting magnetic phases with preferred in-plane and out-of-plane magnetization orientation are identified. The overall switching behaviour is explained by thermal activation of magnetic domains. We show that there is a population of orthogonal bistable magnetic domains, which can be remanently switched between out-of-plane and in-plane orientation by the appropriate magnetic field. This quantity is related to the intersection of the population of states for in-plane and out-of-plane magnetization.

A new and simple method for the preparation of magnetic dot arrays is introduced. Diblock copolymer micelles with a silica core are used as template for the generation of nanostructure arrays. The silica cores are utilized as mask for ion milling preparation. The morphology and size of the silica and magnetic dot arrays are discussed. The magnetic dots are made from Co/Pt multilayer films. Ferromagnetic dots with a diameter well below 20 nm and perpendicular easy axis of magnetization are created. The switching behavior changes from domain wall motion, dominant in the film, to single domain particle switching in the dots. The magneto-optic saturation signals and the evolution of magnetic anisotropy are discussed.

We present a simple method for the production of magnetic antidot arrays utilizing polystyrene-poly-2-vinylpyridine micelles filled with amorphous SiO 2 . By dip coating, a micellar monolayer is deposited onto Co/Pt multilayers. A hexagonal pattern with periodicity of 80 nm is obtained. By Ar + ion etching the micelle layer is transformed into an antidot array due to preferred sputtering of the SiO 2 core. Further ion bombardment transfers the pattern into the magnetic film and leads to a reorientation of the perpendicular to in-plane easy axis which is attributed to intermixing of the Co/Pt multilayers.

We report the fabrication of magnetic films using electron cyclotron resonance ion beam sputtering. The films consist of a Pt buffer layer, a thin magnetic Co layer and a Pt cap. Varying the thickness of the layers, we can tune the magnetic properties and a uniaxial perpendicular magnetic anisotropy can be obtained. Materials like amorphous silicon oxide, amorphous carbon, glass, mica and potassium bromide have been used as substrates. We have analyzed the structure of Co/Pt films on amorphous carbon by means of transmission electron microscopy. The analysis reveals that the buffer layers are polycrystalline with a (1 1 1)-texture, which increases with Pt thickness. The average grain-size is linearly correlated with the total thickness of the Pt buffer layer. While Co grows predominantly in its HCP stacking with c -axis aligned parallel to the surface normal, FCC grains with a strong (1 1 1) texture are also found. Scanning tunneling microscopy investigations reveal an average surface roughness of the Pt buffer layer of 3.0 A . For buffer thickness ⩾ 60 A we find similar magnetic properties for all Co films, not depending on the substrate materials. Co films of 4–8 A thickness exhibit a perpendicular easy axis of magnetization, while a spin reorientation transition is found in a thickness range of 8–13 A. Above 13 A an in-plane easy axis of magnetization is obtained.

The magnetic properties of ultrathin Co films grown on Cu (1 1 13) are investigated by means of the magneto-optic Kerr effect. Applying fields within the film-plane, different ellipticities are found parallel and perpendicular to the step edges. This disparity of the magneto-optical signals in the two perpendicular directions results from a canting of the magnetization that causes a mixing of longitudinal and polar Kerr effect. The canting angle of the magnetization with respect to the surface-plane is calculated. The dependence of the magnetization canting on film thickness is studied systematically.

Magnetization measurements are the classic experimental method to characterize systems of single domain magnetic particles. We consider such particles fixed in space so that the orientation of the magnetization vector of each particle can be influenced by an external magnetic field with respect to characteristic particle directions, i.e. easy directions in the case of anisotropy energy. The aim of this contribution is directed towards experimentalists. We will enhance the well-known idea of the preparation of different low temperature magnetic states (LTMS), introduce the quasi-paramagnetic state which can be reached by the PHFC (positive high field cooling) process, briefly discuss the NHFC (negative high field cooling) and other ways to reach the LTMS. Additionally, our aim is to persuade researchers to consider the susceptibility rather than the magnetization. The most interesting topic is here the pronounced susceptibility maximum which appears in a system of small single domain particles prepared in a LTMS by a PHFC process when measuring in a constant external field versus temperature. We use the susceptibility for an ideal super-paramagnet as a limiting case and consider step by step what are the influences on the susceptibility if the real particle systems exhibit magnetic anisotropy energy, particle-particle interactions and last but not least a particle size distribution.

A new procedure is presented which can be easily applied to separate longitudinal and polar Kerr signals. The method is advantageous particularly in systems where in-plane and out-of-plane states of magnetization are involved in the reversal process. The feasibility of the method is demonstrated at the spin-reorientation transition in Co/Au(1 1 1) films.

Increased blood plasma concentrations of the sulphur amino acid homocysteine (“homocysteinemia”) have been brought into context with neurodegenerative and arteriosclerotic symptoms and diseases. We recently reported on biochemical model reactions on the prooxidative activity of hom ocysteine including the desactivation of Na+/K+-ATPases and hemolysis of erythrocytes (Preibisch et al., 1993). In this communication we extend our model reactions including the oxidation of methionine, metabolization of pyridoxalphosphate and dihydroxyphenylalanine, desactivations of transaminases and peroxidation of low density lipoprotein

A new method to fabricate arrays of ferromagnetic nanostructures is presented which is based on copying the morphology of self-assembled organic layers via ion milling into ferromagnetic Co/Pt multilayers. The self-assembly of diblock copolymer micelles is used. A very flexible tuning of the magnetic properties is possible via the variation of the multilayer composition. The impact of the growth method on the magnetic properties of the multilayer is described and the spin reorientation in Co/Pt discussed. It is demonstrated that arrays of ferromagnetic and superparamagnetic particles can be fabricated with particle sizes < 20 nm. The proposed method gives direct access to the tailoring of magnetic properties of nanosized objects.

We have studied the magnetic domain structure in Permalloy rectangles that reveal flux-closure domain configurations. Arrays with varying spacing between the rectangles are investigated by scanning electron microscopy with polarization analysis as well as by micromagnetic simulation. In contrast to general expectation, rectangles in the flux-closure Landau state show significant coupling and form a magnetic pattern of common chirality. The coupling is due to the stray field that originates from small changes of the magnetization alignment, which is sensitive to the exact shape and the separation of the rectangles.

We study two‐dimensional electron gases subjected to modulated potentials and magnetic fields. With mask techniques it is possible to prepare lateral magnetic superlattices with periods below 100 nm. For a sufficiently strong modulation of the magnetic field at the location of the 2DEG at such small periods, optimized heterostructures with extremely shallow 2DEGs are required. Here, we report on the development of shallow HEMTs containing 2DEGs less than 20 nm below the surface and compatible deposition techniques for the magnetic layers.

Fundamental experiments in magnetism deal with phase transitions. A well-known example is the transition from ferro-to paramagnetism which is commonly observed via the magnetic susceptibility. The susceptibility is defined as the response of magnetization due to the alteration of a magnetic field. Close to the Curie temperature TC the magnetization tends to zero on the average as the ordering effect of the exchange interaction is compensated by the disconcerting action of thermal fluctuations of the spins. Above TC , the ferromagnet becomes paramagnetic. This transition features a very well-pronounced susceptibility peak 1‐ 4 that can be eas

Thermal enhancement has been proven in vitro for the cytotoxic effect of alkylants and platinum compounds, not, however, for etoposide, which acts synergistically to these drugs.Our in vitro study on a neuroblastoma cell line confirmed previous results in other tumor models that the cytotoxicity of etoposide (12.8% as compared to untreated controls) is not enhanced by simultaneous heating to 40 or 42 degrees C for 1 hr (11.9%), as jugded by colony forming assay.The same temperature applied 24 hr before the drug resulted in a significant decrease of colonies (6.1%). Double treatment with etoposide within a 24-hr-interval yielded a similar result (5.6%). The colony number could be further decreased by adding hyperthermia 24 hr before the second treatment (1.3%).We demonstrate in vitro that the enhancing effect of increased temperature on the cytotoxicity of etoposide on neuroblastoma cells is not absent, but depends on scheduling. The temperature range used is achievable in total body hyperthermia. Thus, our results are relevant for possible treatment of disseminated neuroblastoma.

We present a method to separate the longitudinal, polar, and equatorial magnetization components that may contribute to a mixed magneto-optical Kerr-effect signal and demonstrate how the spin-reorientation transition (SRT) can be investigated by means of simple Kerr magnetometry. In a Co/Au(111) film with thickness within the SRT region we find hysteresis loops with nonvanishing remanence in all three components when a field is applied within the film plane. A vertical field, however, drives the same film into a single domain state exhibiting full remanence. The fact that remanence is found in all magnetization components, and full remanence is obtained in a vertical field, rules out that the transition proceeds via a state of canting of magnetization and indicates that it proceeds via a state of coexisting phases.

Various disinfecting drugs (ethacridine lactate, methylene blue, gentian violet, brilliant green, fuchsin acid, cetylpyridinium chloride) were incorporated into CD bead polymers substituted with carboxymethyl groups and a retarded release rate was measured. These polymers were successfully used as sustained release wound powders as well as in chewing gum formulations.

Background Thermal enhancement has been proven in vitro for the cytotoxic effect of alkylants and platinum compounds, not, however, for etoposide, which acts synergistically to these drugs. Procedure Our in vitro study on a neuroblastoma cell line confirmed previous results in other tumor models that the cytotoxicity of etoposide (12.8% as compared to untreated controls) is not enhanced by simultaneous heating to 40 or 42°C for 1 hr (11.9%), as jugded by colony forming assay. Results The same temperature applied 24 hr before the drug resulted in a significant decrease of colonies (6.1%). Double treatment with etoposide within a 24-hr-interval yielded a similar result (5.6%). The colony number could be further decreased by adding hyperthermia 24 hr before the second treatment (1.3%). Conclusions We demonstrate in vitro that the enhancing effect of increased temperature on the cytotoxicity of etoposide on neuroblastoma cells is not absent, but depends on scheduling. The temperature range used is achievable in total body hyperthermia. Thus, our results are relevant for possible treatment of disseminated neuroblastoma. Med. Pediatr. Oncol. 36:197–198, 2001. © 2001 Wiley-Liss, Inc.

The influence of tilted edges on the magnetostatic properties of uniformly magnetized thin rectangular elements is studied. To calculate the magnetostatic energy, the Poisson equation is solved. The shape of the magnetic element is approximated by horizontally assembled thin cuboids and the solutions of Rhodes and Rowlands [Proc. Leeds Phil. Soc. 6, 191 (1954)] are utilized. A second approach is the straightforward integration of the Poisson equation taking into account the trapezoidal shape of the side faces due to the tilted edges. For an adequate number of cuboids, both methods agree very well. It is found that the shape anisotropy of a single magnetic element with tilted edges is reduced compared to that of an ideal cuboid. For a two element system the shape anisotropy competes with the magnetostatic interaction favoring a magnetization orientation parallel to the connecting line of the elements. If the elements are oriented in-line with their short axes, the easy magnetization axis switches at a critical distance between the elements. This distance increases when the elements have tilted edges.

A static photometric ellipsometer allows the measurement of the magneto-optic Kerr effect at a very high signal-to-noise ratio. To gain information about the state of magnetization a mathematical description of the optical components is required. This involves the use of trigonometric functions, e.g., within the Muller calculus. As these are transcendental functions the inversion of the formulae defining the final state of polarization is impossible. The commonly applied linearization is only valid for thin samples with small Kerr angles. For large Kerr angles the nonlinearity of the analyzer setup becomes important. The influence of these nonlinearities on static ellipsometry is studied analytically and numerically. A method is developed to reveal the magnetic properties with high accuracy despite of the nonlinearities due to the optical setup. The applicability of the method is demonstrated for the experimental data obtained from an ion-irradiated iron film on silicon, revealing the magnetic behavior of...

Die Ausdehnung der Wade bei Kompression des Oberschenkels last sich segmentplethysmographisch messen. Aus der Differenz der naturlichen Ausdehnung bei verschiedenen Staudrucken am Oberschenkel und der Ausdehnung unter komprimierenden Masnahmen last sich die Dehnungscharakteristik derselben bestimmen. Dabei zeigte sich, das Kompressionsverbande mit 2 Binden signifikant fester anliegen und weniger nachgeben als ein Verband mit nur 1 Binde, wahrend Kompressionsstrumpfe wesentlich schwacher sind und die Ausdehnung der Wade unter verschiedenen Staustufen nur quantitativ beeintrachtigen.