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  • 1
    Electronic Resource
    Electronic Resource
    Fabrication and properties of heteroepitaxial magnetite (Fe3O4) tunnel junctions (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3282-3284 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Micron-size magnetic tunnel junctions consisting of ferromagnetic Fe3O4 electrodes, with MgO as a barrier layer, have been fabricated on (100) MgO substrates. Reflection high-energy electron diffraction and transmission electron microscopy studies reveal that the Fe3O4/MgO/Fe3O4 trilayers grown by pulsed laser deposition are heteroepitaxial with abrupt interfaces. To achieve different coercivities for the top and bottom Fe3O4 layers, the trilayers are grown on MgO substrates with a CoCr2O4 buffer layer. The junctions exhibit nonlinear current–voltage characteristics and changes in junction resistance with applied field corresponding to the coercivities of the two magnetic layers. However, the observed magnetoresistance (∼0.5% at 300 K, ∼1.5% at 150 K) is much lower than would be expected for a highly spin-polarized system. Possible reasons for the reduced magnetoresistance are discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122745
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetoresistance and Hall effect of chromium dioxide epitaxial thin films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5585-5587 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial CrO2 thin films have been grown on TiO2(100) and Al2O3(0001) substrates by atmospheric pressure chemical vapor deposition. The films have a Curie temperature (Tc) of around 393 K with the ones grown on TiO2 exhibiting in-plane uniaxial magnetic anisotropy. They also display metallic characteristics, with room temperature resistivity of about 285 μΩ cm, dropping by about two orders of magnitude upon cooling down to 5 K. Magnetoresistance (MR) properties of the films have been measured with the magnetic field in the plane. For a field of 40 kOe, a positive transverse MR of about 25% at 5 K and a negative MR of about 7% at near Tc have been observed. In addition, Hall resistivity has been measured with magnetic field up to 40 kOe. A positive ordinary Hall effect is found at low temperatures, indicating the conduction carriers are holes. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369807
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of strain on the magnetic properties of epitaxial (100) chromium dioxide (CrO2) films (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 713-715 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Chromium dioxide (CrO2) films have been grown epitaxially on (100) TiO2 substrates using chemical vapor deposition and their magnetic properties were studied as a function of film thickness (500 Å–1.2 μm). Because of the lattice mismatch with the substrate, the films are strained as evidenced by x-ray diffraction measurements. The amount of strain depends on the thickness and also on the substrate cleaning conditions used prior to growth. Independent of their thickness, the films exhibit a sharp ferromagnetic transition with a Curie temperature in the range of 390–395 K. In-plane magnetic anisotropy is observed for the films, with [001] and [010] being the easy axis and hard axis directions, respectively, for the thicker films. The anisotropy field decreases with decreasing thickness, with the easy and hard axes switching directions for the thinnest films. The results are explained in terms of the competition between magnetocrystalline and strain anisotropies that favor the [001] and [010] magnetization directions, respectively. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124491
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  • 4
    Electronic Resource
    Electronic Resource
    Textured diamond films growth on (100) silicon via electron-assisted hot filament chemical vapor deposition (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1965-1967 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Textured (100) diamond films are successfully grown on single-crystalline (100) silicon substrate by electron assisted hot filament chemical vapor deposition from a gas mixture of methane and hydrogen. The effects of various parameters have been studied. The optimal growth conditions are obtained and the oriental growth character is discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118793
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  • 5
    Electronic Resource
    Electronic Resource
    Extraordinary Hall effect in (111) and (100)-orientated Co/Pt superlattices : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5367-5369 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated a series of (111)- and (100)-orientated Co/Pt superlattices of high quality. (111)-orientated superlattices acquire a perpendicular magnetic anisotropy for samples with thin Co layers whereas for the (100)-orientated superlattices the easy magnetization direction remains in plane. Analysis of the extraordinary Hall effect (EHE) verifies the applicability of simple scaling laws between the resistivity and the EHE coefficient for these layered materials. In addition, we have found a marked dependence of the skew coefficient on Co layer thickness. The contribution to EHE from quantum side-jump remains relatively constant. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364599
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  • 6
    Electronic Resource
    Electronic Resource
    Contrasting magnetic and structural properties of two La manganites with the same doping levels : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7076-7078 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Powder and sintered samples of La0.9MnO3 (LMO) and La0.62Y0.07Ca0.31MnO3 (LYCMO) are used in this study. The two initial calcined in air powders have almost identical ferromagnetic properties with Tc(approximate)250 K, and saturation magnetization of σ(approximate)90 emu/gm corresponding to Mn4+(0.3)/Mn3+(0.7). Heating the calcined powders in argon to high temperatures lowers Tc to (approximate)120 K; however, subsequent oxygen annealing brings back the high Tc form. The LYCMO remains ferromagnetic with σ(approximate)90 emu/gm in both heat treatments but only has a colossal magnetoresistance (MR) for Tc(approximate)120 K. In contrast the LMO with Tc(approximate)120 K has σ reduced to one-half its ferromagnetic value and the MR is almost zero. Neutron diffraction shows only the ferromagnetic structure below Tc for LYCMO but the low magnetization of LMO is best interpreted as a mixed ferro–antiferromagnetic structure rather than a canted one. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367571
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  • 7
    Electronic Resource
    Electronic Resource
    Transport and magnetic properties of epitaxial and polycrystalline magnetite thin films : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7049-7051 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transport and magnetic properties of magnetite (Fe3O4) thin films grown epitaxially on single crystal MgO(100) and SrTiO3(100) substrates, and with multiple grain orientations on polycrystalline SrTiO3 substrates, have been investigated. The films are grown using pulsed laser deposition and their epitaxial quality determined using ion channeling measurements. Transport and magnetic studies of Fe3O4 films as a function of thickness and morphology suggest that epitaxial strain and growth defects affect the width and temperature of the Verwey transition. In addition, these factors also significantly influence the magnetic coercivity of the films. The low-field magnetoresistance (MR) behaviors of epitaxial and polycrystalline films as a function of temperature have been compared and they were found to be quite similar, suggesting very small contribution to the MR from grain boundaries. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367547
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  • 8
    Electronic Resource
    Electronic Resource
    Bias voltage and temperature dependence of magnetotunneling effect : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6515-6517 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied systematically the magnetotunneling properties of several metallic magnetictunnel-junction systems (Ni80Fe20–insulator–Ni80Fe20,Ni80Fe20–I–Co,Co–I–Co, Ni40Fe60–I–Co). The room-temperature magnetoresistance MR value at zero-bias ranges between 16% and 27%, depending on the spin polarization of the electrodes. There seems to be a general bias dependence of MR in all of these systems. In particular, it requires a bias in the range of 0.22–0.23 V to suppress the maximum MR value by half. We have also measured the bias dependence of MR as a function of barrier parameters (thickness and oxidation time). At low temperature, a sharp cusplike feature appears near zero bias. In some cases, low-temperature MR values substantially exceed expectations from established spin-polarization. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367813
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  • 9
    Electronic Resource
    Electronic Resource
    Epitaxial La0.67Sr0.33MnO3 magnetic tunnel junctions : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5509-5511 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the observation of a large magnetoresistance (83%) at low magnetic fields of tens of Oe at 4.2 K in the epitaxial trilayer junction structure, La0.67Sr0.33MnO3/SrTiO3/La0.67Sr0.33MnO3. The spin-polarization parameter of the manganite has been determined from the magnetoresistance value. The switching fields of the two magnetic layers were designed by using the magnetic shape anisotropy. By limiting the sweeping field in a low field range (∼100 Oe), we have achieved bistable resistive states at zero field, which is of potential interest for magnetoelectronic applications. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364585
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  • 10
    Electronic Resource
    Electronic Resource
    Low-field magnetoresistive properties of polycrystalline and epitaxial perovskite manganite films (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1124-1126 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The low-field magnetoresistance (MR) properties of polycrystalline La0.67Sr0.33MnO3 and La0.67CaO33MnO3 thin films with different grain sizes have been investigated and compared with epitaxial films. MR as high as 15% has been observed in the polycrystalline films at a field of 1500 Oe at low temperatures, whereas the MR of the epitaxial films is less than 0.3% in the same field range. Based on the magnetization dependence of the MR, the current-voltage characteristics, and the temperature dependence of the resistivity, we attribute the low-field MR to spin-dependent scattering of polarized electrons at the grain boundaries which serve as pinning centers for the magnetic domain walls. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119747
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