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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The anisotropic magnetoresistance (AMR) has been measured at room temperature on a series of epitaxial iron films of various thicknesses. Seven of the films range in thickness from 5 to 20 nm, and one is 500 nm thick. The resistivity of the films was measured with current along photolithographically defined paths parallel to three directions of high symmetry in the single crystal films ([001], [110], and [111]). It was determined that the magnitude of the AMR depends upon the direction the current is applied and that this directional dependence increases with film thickness until saturating near 20 nm. The AMR is roughly 0.15% for all crystal directions in the thinnest films, while in the thickest film, the AMR is 0.08% with current along the [001] direction, 0.35% along the [110] direction, and 0.51% along the [111] direction. These values are to be compared with the AMR of bulk polycrystalline iron which is 0.2%; a weighted average over the different crystallographic directions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of molecular-beam-epitaxy iron films grown on (001) GaAs substrates were studied using a SQUID magnetometer. In uncapped films, where there is an oxidized iron layer on top of the film, the M-H loops shift from being symmetric about the origin when the film is cooled in applied fields to temperatures below 100 K. The observed behavior is attributed to a unidirectional exchange anisotropy generated by the antiferromagnetic ordering of the oxidized iron surface. By comparing the magnitude of the exchange coupling observed in these films with that observed in the Co-CoO system, the oxide that forms on the iron surface is most likely FeO. In addition, the magnetic training effect or the effect of cycling through the hysteresis loops at fixed temperatures has been studied. It is noted that the temperature dependence of the measured exchange coupling is different from that which is usually reported. The reason for this difference is unknown.
    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 70 (1991), S. 5822-5824 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetotransport properties of iron thin films grown by molecular-beam epitaxy (MBE) have been investigated. The films were grown on (110) GaAs substrates and were allowed to develop a natural oxide. The iron oxide on the free surface is FeO and has an antiferromagnetic transition temperature on the order of 200 K. This antiferromagnetic oxide provides an exchange bias for the iron film at low temperatures. Although it is usual to study exchange coupling with magnetization measurements, we have used the low-temperature magnetotransport properties of the films to study the exchange coupling and compare it to models of this phenomenon.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0533
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The Golgi apparatus (GA) of spinal cord motor neurons is fragmented in sporadic amyotrophic lateral sclerosis (ALS), and in asymptomatic and symptomatic transgenic mice expressing the G93A mutation of the gene of the human Cu,Zn superoxide dismutase, found in certain cases of familial ALS (FALS) [Gonatas NK (1994) Am J Pathol 145 : 751–761; Mourelatos Z, et al. (1996) Proc Natl Acad Sci USA 93 : 5472–5477]. A similar fragmentation of the GA has been described in cells treated with microtubule-depolymerizing drugs, where the organelle is functional and contains both Golgi stacks and trans-Golgi network (TGN), the compartment of exit and targeting of proteins processed by the GA. To gain a better definition of the structure of the fragmented neuronal GA in ALS, four cases of sporadic ALS with numerous Bunina bodies in spinal cord motor neurons were stained with antibodies against human TGN and against the lumenal and cytoplasmic domains of MG160, a protein of the medial cisternae of the GA. The fragmented GA was stained with the three antibodies, indicating the presence of both Golgi stacks and TGN. Furthermore, the staining of the fragmented GA by the antiserum against the cytoplasmic domain of MG160 indicates that the fragmentation of the GA is not the result of a terminal and global cytoplasmic lytic event. The Bunina bodies were not stained by the anti-MG160 antibodies, suggesting that they are not derived from the GA. The perikarya of neurons with fragmented GA showed normal immunoreactivity with antibodies against the heavy neurofilament subunit and α-tubulin. However, because of the lack of appropriate antibodies the localization of proteins such as spectrin, ankyrin, centractin and others which link the microtubules with the GA were not done. The findings support the hypothesis that, in ALS, the fragmented neuronal GA is functional. Additional work with animal models of ALS may establish whether the fragmentation of the GA is a sign of early degeneration or a compensatory reaction of the injured motor neuron.
    Type of Medium: Electronic Resource
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