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Ferromagnetic Material (ferromagnetic + material)
Selected AbstractsScandium-Doped AlN 1D Hexagonal Nanoprisms: A Class of Room-Temperature Ferromagnetic Materials,ANGEWANDTE CHEMIE, Issue 1 2010Weiwei Lei Dr. Mut zur Lücke: Dotieren mit nichtmagnetischen Scandiumionen verringert die Bildungsenergie von Al-Leerstellen in Aluminiumnitrid. Diese Leerstellen sind der Grund für den Raumtemperatur- Ferromagnetismus in eindimensional angeordneten hexagonalen Nanoprismen von AlN:Sc (siehe Mikrograph), wie auch First-Principles-Rechnungen bestätigen. Das Dotieren eröffnet somit einen neuen Zugang zu verdünnten magnetischen Halbleitermaterialien. [source] Design and application of layered composites with the prescribed magnetic permeabilityINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2010Jae Seok Choi Abstract This research aims to design the microstructure with the prescribed magnetic permeability and proposes a design method to control the magnetic flux flow using layered microstructures. In the optimization problem for the microstructure design, the objective function is set up to minimize the difference between the homogenized magnetic permeability during the design process and the prescribed permeability based on the so-called inverse homogenization method. Based on the microstructure design result, a microstructure composed of layered materials is proposed for the purpose of the efficient magnetic flux control. In addition, its analytical calculation is added to confirm the feasibility of the optimized results. The layered composite of a very thin ferromagnetic material is expected to guide the magnetic flux and the performance of the magnetic system can be improved by turning the microstructures appropriately. Optimal rotation angles of microstructures are determined using the homogenization design method. The proposed design method is applied to an example to confirm its feasibility. Copyright © 2009 John Wiley & Sons, Ltd. [source] Influence of the Mn compositional distribution on the magnetic order in diluted GaMnN layersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008D. Mai Abstract GaMnN is a prototypical GaN-based dilute magnetic semiconductor (DMS) and its potential as a room temperature ferromagnetic material is still a controversial question to be answered. Diluted GaMnN layers with Mn concentrations up to several percent have been grown by plasma-assisted MBE on MOVPE-GaN templates either on p-Si(111) or on Al2O3(0001) substrates. None of the samples reported here shows second phase precipitates in XRD or in the TEM analysis. However different composition distributions have been evidenced by EDX during the scanning TEM analysis. GaMnN grown at a substrate temperature of TS = 650 °C exhibits extended structural defects and strong compositional inhomogeneity. This could be indicative of decomposition due to local strain. Samples grown at TS = 775 °C with a Mn concentration of about 3% show a homogeneous Mn distribution in the layer. The magnetic properties are found to vary from spin glass to ferromagnetic behaviour at room temperature among different samples. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] In vitro study of magnetic resonance imaging artefacts of six supraglottic airway devicesANAESTHESIA, Issue 6 2010M. Zaballos Summary We investigated the artefacts created during magnetic resonance imaging by five different laryngeal mask airways: the Classic (cLMAÔ); the LMA ProSealÔ; the LMA UniqueÔ; the Ambu® Disposable Laryngeal Mask; the LMA SupremeÔ; and one other supraglottic airway device, the i-gel supraglottic airway. The devices were placed on top of and inside a phantom simulator to resemble the position in vivo. The artefacts with the cLMA, Unique and Supreme were similar and related to ferromagnetic material in the pilot balloon valve. Artefacts were more prominent with the ProSeal. There were no artefacts with the Ambu Disposable Laryngeal Mask or the i-gel. [source] Self-regulating hyperthermia induced using thermosensitive ferromagnetic material with a low Curie temperatureCANCER SCIENCE, Issue 4 2008Hajime Saito Hyperthermia has been used for many years to treat a variety of malignant tumors. The Curie temperature (Tc) is a transition point at which magnetic materials lose their magnetic properties, causing a cessation of current and thus heat production. The Tc enables automatic temperature control throughout a tumor as a result of the self-regulating nature of the thermosensitive material. We have developed a method of magnetically-induced hyperthermia using thermosensitive ferromagnetic particles (FMPs) with low Tc (43°C), enough to mediate automatic temperature control. B16 melanoma cells were subcutaneously injected into the backs of C57BL/6 mice, after which tumors were allowed to grow to 5 mm in diameter. FMPs were then injected into the tumors, and the mice were divided into three groups: group I (no hyperthermia, control); group II (one hyperthermia treatment); and group III (hyperthermia twice a week for 4 weeks). When exposed to a magnetic field, the FMPs showed a sharp rise in heat production, reaching the Tc in tissue within 7 min, after which the tissue temperature stabilized at approximately the Tc. In groups I and II, all mice died within 30,45 days. In group III, however, 6 of 10 mice remained alive 120 days after beginning treatment. Our findings suggest that repeated treatment with magnetically-induced self-regulating hyperthermia, mediated by FMPs with a low Tc, is an effective means of suppressing melanoma growth. A key advantage of this hyperthermia system is that it is minimally invasive, requiring only a single injection for repeated treatments with automatic temperature control. (Cancer Sci 2008; 99: 805,809) [source] Magnonic excitations versus three-dimensional structural periodicity in magnetic compositesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2006M. Krawczyk Abstract The study deals with the spin wave spectrum in magnetic macrostructure (composed of two ferromagnetic materials) showing a 3D periodicity; the structure considered consists of spherical ferromagnetic grains disposed in the nodes of a simple cubic crystal lattice and embedded in a matrix with different ferromagnetic properties. It is shown that the magnonic spectrum of this composite structure exhibits frequency regions forbidden for magnon propagation, and the energy gaps are sensitive to the exchange contrast between the constituent materials as well as to the magnetization contrast. The widths of the respective magnonic gaps are studied as functions of parameters characterizing the magnetic structure. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural and Magnetic Properties of Various Ferromagnetic NanotubesADVANCED MATERIALS, Issue 45 2009Xiu-Feng Han Abstract The structural and magnetic properties of ferromagnetic nanotubes fabricated by a low cost electrodeposition method are investigated. The fabrication of various elemental ferromagnetic materials are described, such as Fe, Co, and Ni, and ferromagnetic alloys, such as NiFe, CoPt, CoFeB, and CoCrPt nanotube arrays, in aluminum oxide templates and polycarbonate membranes with different diameters, wall thicknesses, and lengths. The structural, magnetic, and magnetization reversal properties of these nanotubes are investigated as a function of the geometrical parameters. The angular dependence of the coercivity indicates a transition from the curling to the coherent mode for the ferromagnetic nanotubes. The results show that nanotube fabrication allows the outer and inner diameter, length, and thickness of the nanotubes to be tuned systematically. The magnetization processes of ferromagnetic nanotubes are influenced by the wall thickness. [source] Evaluation of ferromagnetic shape-memory alloys by the extended Hückel methodIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2007Kei Ehara Student Member Abstract Ferromagnetic shape-memory alloy (SMA) are powerful candidates as actuators, pressure sensors, magnetic sensors, etc. Magnetic-field-induced strain has been observed in many ferromagnetic SMA. The magnetic-field-induced strain is a reversible transformation in the martensite phase with the magnetic field. We have investigated the property of the ferromagnetic shape-memory materials by the extended Hückel method, and estimated the ferromagnetic shape-memory of Fe,Pt and Fe,Pd alloys at high temperatures. We used two physical quantities, i.e. cohesive energy and energy fluctuation, to measure the stability of the materials. On the basis of the cohesive energy and energy fluctuation, we discuss the characteristics of ferromagnetic SMA, in which the energy fluctuation is a measure of thermal stability of the metals and/or alloys. The martensite structure is unstable, which means that the energy fluctuation has to be controlled to a small value to keep the martensite phase. Furthermore, it is estimated that the energy fluctuation is associated with the Curie temperature. The Curie temperature is an essential parameter for ferromagnetic materials. From the discussion presented above, we can propose the following: (i) Alloys possessing a low cohesive energy are associated with a high mobility of atoms and are suitable for ferromagnetic shape-memory materials; (ii) Alloys showing a low energy fluctuation show ferromagnetic shape-memory and are favored for use as memory devices. We found that I (iodine) is the best dopant for Fe,Pt ferromagnetic SMA, and Tc (technetium) is the best dopant for Fe,Pd ferromagnetic SMA. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Moving boundary vortices for a thin-film limit in micromagneticsCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 5 2005Roger Moser We study the limiting behavior of solutions of the Landau-Lifshitz-Gilbert equation belonging to thin films of ferromagnetic materials. In the appropriate time scale and under reasonable conditions, there is a subsequence converging to a map that has vortices at two boundary points. The vortices move Hölder-continuously in time, and the map satisfies a formal Euler-Lagrange equation away from the vortices. © 2004 Wiley Periodicals, Inc. [source] | ||||||||||||||||