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  • Articles  (233)
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  • 1
    Electronic Resource
    Electronic Resource
    Growth of giant magnetoresistance spin valves using Pb and Au as surfactants (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5183-5191 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the use of Pb and Au as surfactants in an attempt to achieve smoother and sharper interfaces in three types of giant magnetoresistance (GMR) spin valve multilayers: symmetric spin valves, bottom spin valves, and top spin valves. The coupling fields are reduced by a factor of 10 for symmetric and bottom spin valves and by a factor of 3 for top spin valves, presumably by suppressing roughness and interdiffusion at the Co/Cu/Co interfaces, when ∼1 monolayer of Pb is deposited in the early stages of spin valve growth. The Pb has a strong tendency to float out or segregate to the surface during deposition of the spin valve leaving the GMR largely unaltered. Au is almost as effective as Pb, however the Au tends to be left behind in the spin valve, and the GMR is reduced slightly. Attempts to use Hg as a surfactant were unsuccessful. The coupling field increased, and the GMR decreased sharply. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363460
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic and thermodynamic properties of Sr2LaFe3O9 : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6608-6610 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the magnetization, specific heat, and 57Fe Mössbauer spectrum are presented for Sr2LaFe3O9. The temperature dependence of the specific heat and magnetization indicates that Sr2LaFe3O9 undergoes an antiferromagnetic transition at TN=203 K. The small entropy removal ΔS and small effective paramagnetic moment μeff suggest an itinerant character for the Fe moment in this compound. In low applied fields, the zero field cooled (ZFC) and field cooled (FC) magnetization below TN exhibit a hysteretic behavior indicating the existence of some ferromagnetic correlation. This behavior is suppressed by high applied fields. The 57Fe Mössbauer spectrum measured at 4.2 K for Sr2LaFe3O9 indicates two superimposed hyperfine fields of 260 and 450 kOe with area ratios of 1/3 and 2/3, respectively, consistent with previous measurements. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361898
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  • 3
    Electronic Resource
    Electronic Resource
    Control of the in-plane epitaxy for bi-epitaxial grain boundary junctions using a new multilayer structure (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4584-4588 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to obtain 100% bi-epitaxial 45° grain boundary junctions of YBa2Cu3Ox (YBCO), we have systematically examined the in-plane epitaxy of CeO2 films grown on MgO substrates. The inevitable presence of CeO2[110](parallel)MgO[100] causes mixtures of in-plane rotation of 0° and 45° between YBCO/CeO2/MgO and YBCO/MgO. We have further developed a new structure, namely YBCO/CeO2/Yttria-stabilized ZrO2/MgO and YBCO/MgO boundary, so that 100% in-plane rotation of 45° can be routinely obtained. The model of the in-plane epitaxial relationship between the multilayers using near coincident site lattices was proposed. The critical current density of the junctions made on the boundary is 3×103 A/cm2 at 77 K, while the order of the Jc of YBCO films on both sides of the grain boundary is 106 A/cm2. The current-voltage characteristics of the junctions show resistively shunted junction behavior. The better epitaxy of our new structure can lead to a better control of grain boundary critical current density. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359557
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  • 4
    Electronic Resource
    Electronic Resource
    Specific heat and magnetization of Co2−xSc1+xSn : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4812-4814 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Co2ScSn crystallizes with the cubic L21 Heusler structure and is an itinerant ferromagnet with Tc=238 K. X-ray diffraction measurements show that Co2−xSc1+xSn retains the L21 crystal structure with an essentially unchanged lattice constant for 0≤x≤0.15. However, Tc determined from the magnetization measurements decreases monotonically with increasing Sc concentration from 238 K for x=0 to 40 K for x=0.11, and then remains at 40 K from x=0.11 to 0.14. The electronic specific heat coefficient γ is enhanced from 13 mJ/mole-K2 for Co2ScSn (x=0) to 30 mJ/mole-K2 for x=0.13 (Co1.87Sc1.13Sn). In addition, the C/T versus T2 plot shows a leveling-off behavior at low temperatures for the x=0.13 sample. The γ enhancement and level-off behavior observed when a system approaches a magnetic instability are discussed in terms of the self-consistent renormalization theory of spin fluctuations for weak itinerant ferromagnets and nearly magnetic systems. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361616
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  • 5
    Electronic Resource
    Electronic Resource
    Optimizing the giant magnetoresistance of symmetric and bottom spin valves (invited) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5277-5281 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have attempted to optimize the values of the giant magnetoresistance in symmetric spin valves of the type NiO/Co/Cu/Co/Cu/Co/NiO (achieving 23.4%) and in bottom spin valves of the type Co/Cu/Co/NiO (achieving 17.0%), the largest values ever reported for such structures. The key elements in this achievement are improved vacuum conditions and careful attention to the film thicknesses. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361352
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  • 6
    Electronic Resource
    Electronic Resource
    The trade-off between large magnetoresistance and small coercivity in symmetric spin valves (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8603-8606 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the use of various alloys as substitutes for pure Co in the center film of symmetric spin valves of the type NiO/Co/Cu/Co/Cu/Co/NiO. The aim of this work is to identify magnetic materials that exhibit smaller coercivities than pure Co for the center or "valve'' film but which retain much of the giant magnetoresistance associated with a pure Co film. The materials investigated include Co95Fe5, Co90Fe10, Ni80Fe20, Co86Fe10.5Ni3.5, and Co85B15. It appears that each of these alloys scatters electrons more strongly than does pure Co as they cross the center film. This scattering degrades the dual spin-valve effect, which is the primary advantage of the symmetric spin valve. As a result, a tradeoff exists between large GMR and small coercivity when using these materials. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362457
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetoresistance values exceeding 21% in symmetric spin valves (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 273-277 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report values of the giant magnetoresistance (GMR) effect exceeding 21% in symmetric spin valves, the highest values ever reported for such structures. The key elements in this achievement are the use of a Co/Cu/Co/Cu/Co multilayer in which the center Co layer is substantially thicker than the outer Co layers and the use of the antiferromagnetic insulator NiO at the top and bottom to pin the adjacent Co layers magnetically. The relative Co layer thicknesses suggest that some specular scattering of conduction electrons may occur at the metal/insulator interfaces and may enhance the GMR. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360692
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  • 8
    Electronic Resource
    Electronic Resource
    Optical and structural characterization of InAs/GaSb superlattices (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 7529-7532 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InAs/GaSb superlattices sandwiched between conventional InAs layers were grown by low pressure metal organic chemical vapor deposition. Period and roughness of the superlattices were examined by field emission transmission electron microscopy. Room temperature infrared absorption spectra for InAs/GaSb superlattices were obtained by Fourier-transform infrared spectroscopy. The effects of varying the doping levels and thicknesses of the InAs sandwiching layers on the absorption spectra of InAs/GaSb superlattices were studied. It was found that by choice of suitable doping levels and cap/buffer thicknesses, the resulting fermi level equalization (as in normal homo or heterojunctions) thereby allowed the setting or "pinning" of the superlattice Fermi level to any desired value within the range made available by the original bulk material characteristics in conjunction with the doping conditions. When the thicknesses of the InAs sandwiching layers became less than 1 μm, the sandwiching effect and the intersubband transition decreased dramatically. The structure of the interfaces inside the superlattice was also studied. Energy dispersive spectroscopy was used to estimate interdiffusion conditions within the superlattice. The effects of different periods and purge gases on the absorption spectra were also studied. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365295
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetization and specific heat studies of Gd2In : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5403-5405 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the temperature and magnetic field dependence of the magnetization for Gd2In. The results show that Gd2In exhibits a helical ferromagnetic transition at 190 K and an antiferromagnetic transition at 100 K in zero and low applied fields. Both the helical ferromagnetic state at temperatures between 100 and 190 K and the antiferromagnetic state at low temperatures are transformed to a simple ferromagnetic state by high applied fields. The antiferromagnetic transition temperature decreases with increasing applied field and approaches zero at H=25 kOe. We have also measured the temperature dependence of the specific heat for Gd2In. The data show two distinct specific heat anomalies which are associated with the two magnetic transitions. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362319
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  • 10
    Electronic Resource
    Electronic Resource
    Oxygen dependence of the Josephson weak link effect, specific heat, and the transition temperature of YBa2Cu3Ox : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5873-5875 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured χ(T) for oxygen-annealed YBa2Cu3Ox samples and observed a glass-like behavior at low magnetic fields which can be explained in terms of a Josephson weak link effect. The glass transition temperature Tg depends on the oxygen annealing temperature and sample pellet pressure. Tg disappears when a sample was powdered after receiving an oxygen anneal, indicating that the Josephson weak link effect occurs between intergranular boundaries. In addition, Tc shifts from 93 K for the air-sintered samples to 90 K for the oxygen-annealed materials. Under vacuum annealing, Tg disappears and Tc first shifts back to 93 K. Prolonged vacuum annealing or vacuum annealing at higher temperatures depresses Tc to below 90 K. The temperature dependence of the specific heat shows a single anomaly for samples sintered in air or annealed under high vacuum. But a double-peak specific heat anomaly occurs for the oxygen-annealed samples. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362157
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