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  • 1
    Electronic Resource
    Electronic Resource
    The extraordinary Hall effect in coherent epitaxial τ (Mn,Ni)Al thin films on GaAs : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6399-6401 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrathin coherent epitaxial films of ferromagnetic τ(Mn,Ni)0.60Al0.40 have been grown by molecular beam epitaxy on GaAs substrates. X-ray scattering and cross-sectional transmission electron microscopy measurements confirm that the c axis of the tetragonal τ unit cell is aligned normal to the (001) GaAs substrate. Measurements of the extraordinary Hall effect (EHE) show that the films are perpendicularly magnetized, exhibiting EHE resistivities saturating in the range of 3.3–7.1 μΩ-cm at room temperature. These values of EHE resistivity correspond to signals as large as +7 and −7 mV for the two magnetic states of the film with a measurement current of 1 mA. Switching between the two magnetic states is found to occur at distinct field values that depend on the previously applied maximum field. These observations suggest that the films are magnetically uniform. As such, τ(Mn,Ni)Al films may be an excellent medium for high-density storage of binary information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352609
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  • 2
    Electronic Resource
    Electronic Resource
    As-deposited high Tc and Jc superconducting thin films made at low temperatures (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 908-910 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 2000 A(ring) as-deposited high Tc superconducting Y1Ba2Cu3O7−x films with zero-resistance temperatures of ∼89 K and critical current densities about 0.7×106 A/cm2 at 77 K have been reproducibly fabricated at a substrate holder temperature of 650 °C, using pulsed laser deposition, with no post-annealing. One key to these results is the injection of gaseous oxygen into the laser-produced plume just in front of the target. In this way, the correct amount of oxygen is incorporated into the as-grown film so that post-deposition treatment becomes unnecessary. The in situ growth of such high Tc and Jc films is an important step in the use of the laser deposition technique to fabricate multilayer structures such as Josephson junctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100155
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  • 3
    Electronic Resource
    Electronic Resource
    Two-dimensional modulated ferrimagnetic systems (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4903-4903 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bi2Sr2MnOy, isomorphic to the high-Tc compound containing Cu, exhibits a displacement modulation driven by the bending of Bi double layers, thus creating a modulated environment for the magnetic MnO2 layers which are 12 A(ring) apart. Neutron scattering results will be presented, showing antiferromagnetic order in zero field and a field-induced transition to weak ferromagnetism. This behavior is a direct consequence of the structural modulation which breaks the symmetry of two otherwise equivalent ordering directions of (010) and (100)−the latter being associated with weak ferromagnetism. Magnetic scattering has been observed at superlattice positions, suggesting that the displacement modulation affects the valence of the magnetic ions. Subtle differences in magnetic behavior are observed in similar compounds where Pb is substituted for Bi and Ca for Sr. These results will be discussed in terms of a modulated magnetic model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348950
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetotransport in magnetic epitaxial metal layers buried in (Ga,Al)As heterostructures (invited) (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6117-6117 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Incorporation of magnetic, metallic quantum wells in semiconductors has added new dimensions to epitaxial heterostructures. Magnetotransport experiments explore the interplay of bandstructure, quantum confinement, dimensionality and magnetism. Rare earth monoarsenides, like ErAs, have been grown as buried layers in GaAs. The material is a semimetallic antiferromagnet that exhibits spin-disorder scattering at the Néel point. By diluting the ErAs with ScAs, lattice matching to GaAs can be achieved and these materials exhibit Shubnikov–de Haas (SdH) oscillations. The exchange interaction between the conduction band and the 4f spin deduced from SdH agrees with that derived from spin-disorder scattering. Surprisingly, down to 2 monolayers, quantum confinement does not convert the semimetal into a semiconductor. This is not understood. But, the Neel point can be seen to drop by a factor of two by following the spin-disorder scattering. In the few monolayer regime the magnetotransport can change its character and is more aptly described by bound magnetic polarons. More recently, ferromagnetic, metastable, τ-MnAl layers have also been grown on GaAs. Thin layers of τ-MnAl grow in such a way that the tetragonal axis is perpendicular to the interface. The extraordinary Hall effect and longitudinal magnetotransport confirm that the moment has the desired property of being oriented perpendicular to the interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347785
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  • 5
    Electronic Resource
    Electronic Resource
    Transport in reversibly laser-modified YBa2Cu3O7−x superconducting thin films (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1802-1805 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A focused argon ion laser beam in a controlled ambient is used to modify the transport properties of superconducting YBa2Cu3O7−x thin films. The laser-modified region shows a sharp transition temperature (Tc≈76 K) that is reduced from the unmodified regions of the film (Tc≈87 K). In situ monitoring of the room-temperature electrical resistance is used to control the laser processing and prevent formation of the semiconducting phase. The original properties of the superconducting film can be recovered by plasma oxidation indicating that the laser-induced phase is oxygen deficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342911
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  • 6
    Electronic Resource
    Electronic Resource
    Substrate effects on the properties of Y-Ba-Cu-O superconducting films prepared by laser deposition (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4591-4598 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting thin films of Y1Ba2Cu3Ox with superconducting transition temperature (Tc) near 90 K have been prepared by a laser deposition technique. We show that films prepared on sapphire, lithium niobate, and strontium titanate under identical processing conditions exhibit different electrical characteristics. The film surfaces, interfaces, and crystallinity have been studied by a number of analytical techniques. We conclude that the substrate influences the film properties primarily in three ways: the thermal expansion mismatch introduces cracks in the film, the interface reaction changes the film composition, and the substrate lattice influences the crystallographic orientation of the film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340136
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  • 7
    Electronic Resource
    Electronic Resource
    Growth morphology of epitaxial ErAs/GaAs by x-ray extended range specular reflectivity (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2060-2062 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth morphology of ErAs on [001] GaAs with thicknesses ranging from 2 atomic layers to 400 A(ring) is investigated using x-ray specular reflectivity. This epitaxial system displays rich morphological behavior and we observe the evolution from discontinuous to continuous layers at just a few monolayers and qualitative changes occur in layer thickness fluctuations for thicker films having high dislocation densities. We also demonstrate that the reflectivity of a heteroepitaxial system can be measured and modeled over an extended angular range, starting from grazing angles and continuing through the regions of Bragg scattering at higher angles. Disorder in epitaxial layers typically gives a mosaic line broadening transverse to the reflectivity and we show that transverse line shape considerations are crucial to these measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108306
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  • 8
    Electronic Resource
    Electronic Resource
    Lattice-matched Sc1−xErxAs/GaAs heterostructures: A demonstration of new systems for fabricating lattice-matched metallic compounds to semiconductors (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 382-384 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Successful growth of lattice-matched Sc1−xErxAs layers buried in GaAs with a room-temperature resistivity of ∼50 μΩ cm demonstrates the feasibility of fabricating heterostructures of lattice-matched rare-earth monopnictides and monochalcogenides in semiconductors. Reflection high-energy electron diffraction oscillations during ScAs, ErAs, and Sc1−xErxAs growth indicate monolayer-by-monolayer growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102792
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  • 9
    Electronic Resource
    Electronic Resource
    X-ray scattering study of lattice relaxation in ErAs epitaxial layers on GaAs (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1602-1604 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of a high-resolution x-ray scattering study of the lattice relaxation in [001]ErAs epitaxial layers grown on [001]GaAs. Three thickness regimes are found. ErAs is pseudomorphic on GaAs for thicknesses below 70 A(ring) and between 70 and 300 A(ring) lattice relaxation is observed concomitant with an increase of the in-plane mosaic due to the formation of misfit dislocations. Above 300 A(ring), the out-of-plane transverse scattering from the ErAs lattice planes is no longer specular and further relaxation appears to be related to the out-of-plane mosaic. The ratio of elastic constants, C12/C11, is measured to be 0.126. Thin-film interference oscillations are observed and modeled, finding that for 140 A(ring) of ErAs the interface fluctuations are ∼2.5 monolayers. ErAs/GaAs is an ideal system for x-ray scattering studies of lattice relaxation and structure in epitaxial layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105138
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  • 10
    Electronic Resource
    Electronic Resource
    Hydrogen in Nb/Ta superlattices (1989)
    Springer
    The European physical journal 74 (1989), S. 457-473 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The structural and thermodynamic properties of hydrogen dissolved in Nb/Ta superlattices are studied by in-situ x-ray scattering techniques. From the x-ray satellite intensities, it is found that H induces a strain modulation exhibiting a Curie-Weiss temperature dependence. The intensities are analyzed in terms of a mean field model of the modulated lattice gas, yielding quantitative information on the hydrogen-metal and hydrogen-hydrogen interaction energies. Critical behavior associated with a gas-liquid transition is also observed. Hydrogen density fluctuations with wavelengths shorter than a superlattice period are, however, suppressed by the superlattice, which represents a novel manifestation of a coherent phase transition. These experiments provide new and fundamental insight into the role of spacially varying two body interactions in critical phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01311393
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