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  • 11
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6892-6894 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We studied epitaxially grown single-crystalline chemically disordered ultrathin NixPd1−x alloy films on Cu3Au(100) by means of photoemission using magnetic circular dichroism in the angular distribution. We clearly observe a well-defined three-dimensional band dispersion in 15 monolayer films. On the basis of relativistic selection rules, this dispersion can be related to specific electronic states. Since the spin–orbit coupling (ΔEso) is smaller for Ni than for Pd, the alloy will assume an average value. We find that this average spin–orbit coupling clearly shows up in the electronic structure and correlates directly to the composition of the NiPd alloy film. The results are discussed in terms of a simple qualitative model. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7113-7115 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnitude of the giant magnetoresistance (GMR) observed in multilayers is known to change irreversibly at elevated temperatures. To improve the thermal stability of devices, a fundamental understanding of the GMR and its correlation to the temperature-induced structural and morphological changes in a given system is mandatory. We therefore investigated the structural and magnetic properties of sputtered Co/Cu multilayers in the pre- and postannealed states (temperature regime for annealing up to 750 °C) by in situ x-ray diffraction, transport measurements, ferromagnetic resonance (FMR), and magneto-optical Kerr effect (MOKE). We were able to identify a sequence of distinct structural changes each of which sets in above a characteristic critical temperature. These critical temperatures depend strongly on the thickness of the individual layers. The structural alterations observed range from interfacial sharpening through texture reorientations up to the formation of a granular state, and are associated with distinct in/decreases of the GMR signal. Using FMR and MOKE we determined in-plane magnetic anisotropies and interlayer coupling for as-grown and annealed samples. © 2001 American Institute of Physics.
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  • 13
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 8169-8174 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the effect of the dipolar magnetic coupling (also known as Néel coupling or "orange-peel" coupling) in tunneling magnetoresistive (TMR) elements. With an in situ scanning tunneling microscope we directly accessed the roughness of the films and found a close correspondence between the values for the coupling fields determined by the magneto-optical Kerr effect and the ones computed on the basis of the measured morphology parameters. We confirm an increase of the dipole coupling between the magnetic layers with decreasing barrier thickness as predicted by the model. Deviations from the theoretical predictions are observed for the case of thinner soft magnetic layers, which can be explained by reduced magnetization in very thin films. We demonstrate the importance of dipolar coupling for understanding the magnetic behavior of TMR elements by comparing TMR curves for optimized and nonoptimized structures. © 2001 American Institute of Physics.
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  • 14
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Conventional techniques of magnetic domain imaging are usually not selective with respect to the chemical species in a system under investigation. This limitation can be overcome by employing soft x-ray magnetic dichroism which combines both magnetic sensitivity and chemical selectivity. We present first results on magnetic domain imaging at surfaces obtained with a newly developed photoelectron emission microscope using magnetic circular dichroism (MCD). Topographic studies on a silicon surface showed the instrument to be capable of a lateral resolution of better than 50 nm. Two approaches of separating chemical and magnetic information are demonstrated for Permalloy micropatterns on silicon. First, the lateral distribution of the different chemical species or the magnetic domains is obtained by subtracting images taken at different photon energies (spectromicroscopy). Second, a "small spot" mode permits the acquisition of x-ray absorption spectra from surface areas of less than 2 μm diameter. The latter technique is called microspectroscopy. On a Fe(100) whisker surface we observed magnetic domains with domain boundaries ∼300 nm wide. This value corresponds to the intrinsic width of a 180° domain wall at the surface, as determined by scanning electron microscopy with spin polarization analysis.1 The studies in Ref. 1 have also shown that this kind of domain wall behaves Neél-like at the surface, i.e., the magnetization vector M rotates within the film plane over the domain boundary. Exploiting the directional characteristics of MCD we can map the component of M normal to the domain boundary and thus selectively image the wall itself. © 1997 American Institute of Physics.
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  • 15
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrathin films of 3d-transition metal alloys, and in particular FeCo alloys, currently receive considerable interest because of their potential technological application and the possibility to adjust magnetic properties via the variation of composition and structure. To study magnetic and structural properties of the otherwise unstable fcc phase of FeCo, this structural phase was stabilized by epitaxial growth on Cu(001). Ultrathin FexCo1−x films were deposited at room temperature by coevaporation from two separate Knudsen cells, operated under stabilized conditions. The film thickness was varied between 2 and 9 monolayers (ML) and the Fe concentration between x=0.2 and x=0.95. The growth process was monitored by medium energy electron diffraction (MEED). Auger electron spectroscopy and low energy electron diffraction (LEED) were employed to analyze the composition and structure of the films. A nearly perfect layer-by-layer growth up to at least 9 ML, as seen by MEED, is encountered for x≤0.7. For higher Fe concentrations and thicknesses greater than 4 ML, deviations from the layer-by-layer growth are observed, indicating a structural rearrangement. LEED-I(V) curves reveal the coexistence of two structural phases with different interlayer spacings, the relative amount of which depends on the composition. Magnetic properties were characterized by the magneto-optical Kerr effect (MOKE). The remanent magnetization was found to lie within the film plane over the whole range of thicknesses and concentrations investigated.A linear increase of the Kerr signal at saturation magnetization with increasing thickness indicates that practically the whole film is magnetic. As a function of composition, the saturation Kerr signal develops continuously with increasing Fe content. This suggests that in fcc FeCo alloys the contribution of Fe and Co to the total magnetic moment is nearly constant over the whole compositional range. © 1996 American Institute of Physics.
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  • 16
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization behavior of ultrathin (3 ML) epitaxial Co(001) films on Cu(1 1 13) terraced surfaces was studied in situ using magneto-optic Kerr effect. The films show easy magnetization along the steps. Unusual hard axis Kerr loops (H perpendicular to the steps and in the surface plane) are observed near room temperature and evolve at higher temperature (127 °C) toward the soft magnetic behavior more typical of the easy axis loops observed on the same films. A model is postulated for the behavior that includes a fourfold in-plane anisotropy and a uniaxial in-plane anisotropy of possibly magnetoelastic (ME) or magnetostatic (MS) origin.
    Type of Medium: Electronic Resource
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  • 17
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the novel effect of magnetic dichroism in core level photoemission from ferromagnets with circularly polarized synchrotron radiation in the soft x-ray range. Depending on the relative orientation of photon spin and sample magnetization (parallel or antiparallel), a single core level emission line may be resolved into two lines of different intensities. The mechanism is shown to be due to spin-selective dipole transitions from exchange-split core levels in the presence of spin-orbit interaction. Experiments on the 2p1/2 and 2p3/2levels of Fe are compared to fully relativistic photoemission calculations. Rather good qualitative and quantitative agreement is found. The effect does not rely on the spin-split empty density of states near the Fermi energy, but probes the exchange splitting of core levels directly. Because of its surface sensitivity, x-ray dichroism in photoemission may serve as a new powerful tool in surface and interface magnetism.
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  • 18
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5951-5956 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spin valve systems are widely considered in magnetic rotation angle sensors. We present a simple magnetostatic model to simulate the electrical and magnetic signal of typical spin valve systems as a function of external magnetic field and rotation angle. To match simulation and experiment only a few parameters are needed, which can be determined by a single measurement. Two types of systems are treated and discussed: a simple spin valve and a spin valve with an "artificial antiferromagnet," often used to enhance the exchange bias. The model shows a very good correspondence of the predictions to the experimental results of the systems investigated. In order to quantitatively compare experiment and model, we introduce a useful concept to quantify the quality of the angle rotation curves: the total harmonic distortion. © 2002 American Institute of Physics.
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  • 19
    Publication Date: 2014-05-30
    Description: Author(s): C. von Korff Schmising, B. Pfau, M. Schneider, C. M. Günther, M. Giovannella, J. Perron, B. Vodungbo, L. Müller, F. Capotondi, E. Pedersoli, N. Mahne, J. Lüning, and S. Eisebitt Ultrashort, coherent x-ray pulses of a free-electron laser are used to holographically image the magnetization dynamics within a magnetic domain pattern after creation of a localized excitation via an optical standing wave. We observe a spatially confined reduction of the magnetization within a coup... [Phys. Rev. Lett. 112, 217203] Published Thu May 29, 2014
    Keywords: Condensed Matter: Electronic Properties, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 20
    Publication Date: 2015-03-04
    Description: East–Southeast Asia is currently one of the fastest urbanizing regions in the world, with countries such as China climbing from 20 to 50% urbanized in just a few decades. By 2050, these countries are projected to add 1 billion people, with 90% of that growth occurring in cities. This population shift parallels an equally astounding amount of built-up land expansion. However, spatially-and temporally-detailed information on regional-scale changes in urban land or population distribution do not exist; previous efforts have been either sample-based, focused on one country, or drawn conclusions from datasets with substantial temporal/spatial mismatch and variability in urban definitions. Using consistent methodology, satellite imagery and census data for 〉1000 agglomerations in the East–Southeast Asian region, we show that urban land increased 〉22% between 2000 and 2010 (from 155 000 to 189 000 km 2 ), an amount equivalent to the area of Taiwan, while urban populations...
    Print ISSN: 1748-9318
    Electronic ISSN: 1748-9326
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering
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