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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4733-4733 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Giant magnetoresistance (GMR, large negative and isotropic magnetoresistance) arising from a spin-dependent tunneling effect has been found in metal–nonmetal granular systems exhibiting extremely high electrical resistivities. These granular materials are reactively sputtered Co–(Al, Si)–O and Fe–Mg–O thin films, having a two phase nanostructure consisting of the Co (or Fe) rich metallic and magnetic grains and the Al (or Si,Mg) oxide narrow intergrains. These films possess large specific electrical resistivities(ρ0) of 104–106 μΩ cm at room temperature, and show remarkable magnetoresistance (Δρ/ρ0) whose values are about 8% in maximum at room temperature and at about 10 kOe of applied magnetic field. With decreasing temperature, Δρ/ρ0 and ρ0 increase. The temperature dependence of ρ0 can be expressed in terms of log ρ0∝T−1.2, and the electrical current versus applied electrical voltage does not follow the ohmic low. We consider that a spin- dependent tunneling conductance in the path of magnetic grains–nonmetallic intergrains–magnetic grains is responsible for the observed GMRs accompanying high electrical resistivities. The details of these transport properties and the related magnetization and structural properties will be presented. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5130-5135 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure and properties of Co–N and Co–O based films, prepared by rf magnetron reactive sputtering using nitrogen or oxygen and argon gases, have been studied. Transmission electron microscopy (TEM) observation reveals that each Co–(Al or Si)–(N or O) film is a typical film with granular structure, with grain size less than 5 nm. It is found by micro-focused energy-dispersive x-ray and electron energy loss spectroscopy analysis that the grains are mainly composed of Co and the intergranular regions are ceramics of N or O. In Co–N based films, soft magnetic properties are found in both Si and Al containing films over a wide range of film preparation conditions and compositions. Only the films with Al show soft magnetic properties in Co–O based films, which have ρ of 500–1000 μΩ cm, Hk of about 80 Oe and Bs of about 10 kG. By adding about 10 at. % Pd, the soft magnetic properties and Hk of Co–O based films are significantly improved, with Hk more than 180 Oe. These films exhibit a remarkable constant frequency response of the permeability up to around 500 MHz, which is approximately explained by the Landau–Lifshitz formula. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4574-4576 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the magnetic properties of (Co1−xFex)–Al–O granular thin films prepared by a reactive sputtering method in an atmosphere of O2+Ar. The coercivity and electrical resistivity of the films are almost independent of x, but with increasing x the anisotropy field decreases linearly and the saturation induction has a broad maximum of 20 kG around x=0.7. The granular films show the same general tendency as bulk Co–Fe alloys in the compositional dependence of magnetostriction (λ). The magnitude of λ varies with increasing annealing temperature. Using a film with x=0.08 as the core of a spiral-wound inductor gave a quality factor Q=25 at a frequency of 300 MHz. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd
    Histopathology 28 (1996), S. 0 
    ISSN: 1365-2559
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Histiocytic necrotizing lymphadenitis, also called Kikuchi-Fujimoto (KF) disease, is a benign disorder characterized histologically by paracortical necrotic foci surrounded by histiocytic aggregates. We analysed affected lymph node tissues from 34 patients with the disease in an attempt to elucidate its histogenesis. The ‘necrotizing’ cells showed typical apoptotic changes, including cell shrinkage and condensed and fragmented nuclei. Apoptotic bodies with a peculiar ultrastructure were demonstrated, and DNA fragmentation was detected in these cells by in situ end labelling. Immunostaining for the apoptosis-regulating proteins bcl-2, bax, c-myc and p53 failed to show their involvement in KF disease. However, perforin, a killer cell-specific cytolytic protein essential for provoking apoptosis in target cells, was found to be expressed abundantly by the infiltrating cells, which were thought to be cytotoxic T-lymphocytes. Perforin-expressing cells were present in the apoptotic foci of 28 of the 34 patients (82.4%). Virtually no cells containing perforin granules were present in non-pathological regions, lymph node tissues from control subjects with reactive or tuberculous lymphadenitis or those from patients with KF disease with negligible apoptosis. Therefore, the ‘necrosis’ associated with KF disease appears to be attributable to trans apoptotic death of the killer cell target in the affected nodes. We propose that KF disease should be called apoptotic lymphadenitis.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 659-666 
    ISSN: 0142-2421
    Keywords: XPS ; nanogranular materials ; Co-Al-N ; magnetic materials ; thin film ; nano-composite ; x-ray diffraction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Thin (Co0.8Al0.2)100-xNx (x=0-30 at.%) alloy films prepared by a reactive radio frequency (r.f.) sputtering method were characterized by XPS and x-ray diffraction (XRD). The film with no nitrogen consisted of a CsCl-type CoAl metallic compound, while the nitrogen-containing alloys were composed of very fine AlN and face-centred cubic (fcc) Co phases. The quantitative XPS analysis under an assumption of uniform distribution of all the elements resulted in much lower concentrations of Co and higher concentrations of Al and N in comparison with the bulk composition for the nitrogen-containing alloys. By taking account of the granular structure of the alloy films, i.e. the nanoscale particles of fcc Co embedded in the AlN compound, the results of quantitative XPS analysis were explained successfully. Moreover, the thickness of the AlN layer and the size of the fcc Co particles were also able to be estimated under the nanoscale structure models. The results were in good agreement with observation by transmission electron microscopy, especially when a nanostructure model was adopted where nanoscale Co-N particles are dispersed in AlN matrix in a simple cubic-like arrangement. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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