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  • 1
    Electronic Resource
    Electronic Resource
    Giant magnetothermopower and giant magnetoresistance in molecular beam epitaxy grown Co/Cu(111) superlattices : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5521-5523 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the observation of a giant magnetothermopower (GMT), giant magnetoresistance (GMR), and on magnetization measurements in Co/Cu[111] superlattices grown by molecular beam epitaxy. The maximum value of the GMT (at room temperature) was 14% for a Cu thickness of 9 A(ring) and the maximum GMR (at 4.2 K) was −26% at 7 A(ring) of Cu. Oscillations in the remnant magnetization and the saturation field as a function of Cu thickness with a period of about 10 A(ring) were observed. However, there were no oscillations in the GMT or the GMR. The maximum values of both the GMT and GMR are associated with saturation fields in excess of 40 kOe and with small remnant magnetizations. These results are consistent with the presence of antiferromagnetic coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353689
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  • 2
    Electronic Resource
    Electronic Resource
    A magneto-optic technique for studying magnetization reversal processes and anisotropies applied to Co/Cu/Co trilayer structures : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6368-6370 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the magnetization reversal and magnetic anisotropy behavior of ultrathin Co/Cu(111)/Co (dCu=20 and 27 A(ring)) trilayer structures prepared by MBE on a 500-A(ring) Ge/GaAs(110) epilayer. We describe an arrangement in which the magnetization components parallel and perpendicular to the applied field are both determined from longitudinal MOKE measurements. For the samples examined, coherent rotation of the magnetization vector is observed when the magnetic field is applied along the hard in-plane anisotropy axis, with the magnitude of the magnetization vector constant and close to its bulk value. Results of micromagnetic calculations closely reproduce the observed parallel and perpendicular magnetization loops, and yield strong uniaxial magnetic anisotropies in both layers while the interlayer coupling appears to be absent or negligible in comparison with the anisotropy strengths. An absence of antiferromagnetic (AF) coupling has been observed previously [W. F. Egelhoff, Jr. and M. T. Kief, Phys. Rev. B 45, 7795 (1992)] in contrast to recent results, indicating that AF coupling [M. T. Johnson et al., Phys. Rev. Lett. 69, 969 (1992)] and GMR [D. Grieg et al., J. Magn. Magn. Mater. 110, L239 (1992)] can occur in Co/Cu(111)/Co structures grown by MBE, but these properties are sensitively dependent on growth conditions. The absence of coupling in our samples is attributed to the presence of a significant interface roughness induced by the Ge epilayer. The uniaxial anisotropies are assumed to arise from strain or defects induced in the film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352651
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  • 3
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance of molecular beam epitaxially grown Co-Cu superlattices that exhibit large magnetoresistance : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6381-6383 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The 59Co NMR has been measured for superlattices of Co(15 A(ring))/Cu (7 or 18 A(ring)) grown with either a Au or Cu buffer layer between the substrate and the superlattice. As was reported earlier the Co (15 A(ring))/Cu (7 A(ring)) (Au) superlattice has the largest magnetoresistance (ΔR/R∼26%) known for a MBE grown Co/Cu multilayer. The NMR measurements show that the Au-based superlattices have very flat interfaces and (111) orientation, two features which were supposed to preclude a large value of ΔR/R, and that the average strain in the Co layers is greater for a Au than a Cu buffer layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352657
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  • 4
    Electronic Resource
    Electronic Resource
    Giant magnetoresistance in melt-spun Cu87Co13 : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6546-6547 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results for the temperature and magnetic-field dependence of melt-spun Cu87Co13 are presented and discussed. The magnetoresistance of the as-spun sample exhibits superparamagnetic behavior with a magnetoresistance of 18% at 0.4 K and in a field of 80 kOe. The magnetic-field dependence of the magnetoresistance is approximately proportional to the Langevin function. The microstructure of the sample was investigated by transmission electron microscopy and it appears that the giant magnetoresistance is due to the presence of small Co precipitates with an approximate mean diameter of 12 A(ring) and a mean separation of 35 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356943
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  • 5
    Electronic Resource
    Electronic Resource
    Field dependence of nuclear magnetic resonance in molecular beam epitaxy grown Co(111)/Cu multilayers : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6504-6506 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An initial study of the field dependence of 59Co nuclear magnetic resonance (NMR) has been undertaken for two Co/Cu(111) multilayer films grown by molecular beam epitaxy. The multilayer structure of the films was nominally identical, [Co(15 A(ring))/Cu(7 A(ring))]×20, however by growing the multilayers with similar structures on different buffer layers, Cu(200 A(ring)) and Au(10 A(ring)), saturation magnetoresistances ΔR/R of 4% and 22%, respectively, were obtained. The NMR signal in ferromagnetic materials arises due to the enhancement effect from the electronic magnetization. This enhancement effect is therefore a function of the domain structure and any external magnetic field. By applying a simple model of how the NMR enhancement factor varies with applied field, in the absence of a domain structure, the anisotropy fields at the interfaces and in the bulk were determined separately at T=4.2 K. These were then compared with the coercive field obtained from magnetization measurements. Our results show that at low temperature the anisotropy field at the interfaces is approximately equal to the coercivity obtained from magnetization measurements (260 Oe), while in the bulk the anisotropy field was found to be ∼550 Oe for the low magnetoresistance sample with ΔR/R=4%, and ∼1230 Oe for the high magnetoresistance sample with ΔR/R=22%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358243
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  • 6
    Electronic Resource
    Electronic Resource
    Using magnetoresistance to investigate magnetic interface anisotropy : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4476-4478 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ability to grow high quality thin metallic layers has brought about the discovery of the giant magnetoresistance (GMR) in multilayers and equally the perpendicular anisotropy exhibited by certain ferromagnetic thin films such as Co. In this article, we will describe magnetoresistance and magneto-optical Kerr effect (MOKE) measurements of molecular beam epitaxy-grown multilayers of Co/Cu(111). It is demonstrated that by controlled doping of the interface between the Co and Cu with submonolayer amounts of Au we are able to increase the magnitude of the GMR. Analysis of MOKE data shows that there is an increase in the perpendicular anisotropy of the Au-doped samples compared to those without Au which can account for the increase in the GMR. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364983
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  • 7
    Electronic Resource
    Electronic Resource
    MO polar Kerr studies of Co rich molecular beam epitaxy grown Au/Co multilayers : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6783-6785 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magneto-optical (MO) polar Kerr rotation and ellipticity (PKR and PKE, respectively) of Co rich Au(111)/Co(0001) multilayers grown by molecular beam epitaxy on GaAs(110) substrates are reported. The individual layer thicknesses, tAu and tCo were tAu/tCo=2.6/3.2, 1.0/1.5, and 0.65/0.8 nm. The samples displayed perpendicular magnetic anisotropy smaller than demagnetization energy. PKR and PKE were measured at photon energies between 1.5 and 5.2 eV. In the multilayer with tCo=1.5 nm, PKR at 3.1 eV reached a value of −0.34°, remarkably higher than that reported on Au rich multilayers. The spectra were compared with theory. A satisfactory agreement was obtained only for the sample with the largest bilayer thickness, tAu+tCo=5.8 nm. This indicates that when tAu and tCo are reduced to a few atomic monolayers the role of interfaces is increased. The effects of strain, defects, and atomic mixing at Au-Co interfaces become more important. Both the magnetic and optical properties are modified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356829
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  • 8
    Electronic Resource
    Electronic Resource
    The effect of Au impurities at the interfaces on the magnetoresistance of MBE-grown Co/Cu multilayers : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7055-7057 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have grown Co/Cu multilayers by MBE using a shuttering arrangement wherein half of the sample receives an amount of Au impurities at each interface. Under these controlled conditions, the differences in measurements between each half is attributed only to the effect of the impurities. The samples were characterized by x-ray diffraction and RHEED. We have found that small fractions of a monolayer of Au deposited at the Co/Cu interface significantly decreased the GMR. These results are discussed in the light of current theories on the role of bulk and interface scattering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356724
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  • 9
    Electronic Resource
    Electronic Resource
    Engineering upstream transcriptional and translational signals of Bordetella pertussis serotype 2 fimbrial subunit protein for efficient expression in Escherichia coli: in vitro autoassembly of the expressed product into filamentous structures (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 4 (1990), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Escherichia coli containing a cloned gene encoding the Bordetella pertussis serotype 2 fimbrial subunit failed to produce detectable levels of the gene product in whole-cell extracts. To engineer plasmids capable of directing the expression in E. coli of high levels of this product, both as a pre-protein and as a methionylated mature form the upstream signals of the fimbrial subunit gene were replaced by the lambda PL and PR promoters and the E. coli atpE translational initiation region. These constructs did not result in the expression of fimbrial subunit at detectable levels in several E. coli strains including DH5. However, they did in E. coli CAG629, which is Ion protease and heat shock protein deficient. Both pre-protein and methionylated mature protein had molecular weights of 25.0 kD, which indicated that correct processing of the leader sequence had occurred and thus that it was transposed across the inner membrane. Electron microscopic investigation of the cell surface of E. coli cells expressing either form of the fimbrial gene failed to detect the presence of filamentous structures. The methionytated mature form of the recombinant fimbrial subunit was purified to apparent homogeneity. After dialysis in appropriate conditions it was seen to autoassemble into protein polymers. Antibodies raised against polymerized recombinant subunit reacted weakly with whole B. pertussis serotype 2 fimbriae in immunodot blot assays. However, such antibodies reacted in Western blots equally well with the recombinant and wild-type form of the fimbrial subunit. These results suggest that the assembly in E.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1990.tb02013.x
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  • 10
    Electronic Resource
    Electronic Resource
    Cloning and characterization of an albicidin resistance gene from Klebsiella oxytoca (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 2 (1988), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A DNA fragment containing a gene for resistance to the antibiotic albicidin was isolated from Klebsiella oxytoca and shown to be expressed in Escherichia coli, where it also protected bacteriophage T7 replication from inhibition by albicidin. In vivo translation analysis demonstrated that the cloned 2.2kb DNA fragment coded for a 36 kiloDalton (kD) protein and a 25 kD protein.The DNA sequence was determined for a 654-base-pair open reading frame contained within a 1.2 kb subcloned DNA fragment encoding albicidin resistance. The predicted molecular weight of the polypeptide translated from the open reading frame was 25.8 kD. A putative Shine-Dalgarno sequence precedes the open reading frame but a potential promoter sequence was not detected. A possible rho-independent transcription termination signal was found directly following the stop codon. The functional protein for albicidin resistance was isolated and purified. Both the molecular weight and NHg-terminal amino acid sequence of this protein correspond with that predicted from the DNA sequence of the open reading frame. The cloned albicidin resistance gene had no effect on the tsx (nupA) nucleoside uptake gene associated with spontaneous albicidin resistance in E. coli; also, it did not complement any of a range of E. coli DNAts mutants at restrictive temperatures. The cloned resistance gene product remained intracellular in exponential cultures of K. oxytoca and E. coli. Cell-free extracts from E. coli containing the resistance gene protected a sensitive strain of E. coli from inhibition by albicidin, as did the purified albicidin resistance protein. The mechanism of this albicidin resistance protein involved binding to albicidin to form a complex without antibiotic activity, but without catalysing further chemical modification of the antibiotic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1988.tb00050.x
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