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  • 1995-1999  (22)
  • 1985-1989  (28)
  • 1960-1964  (2)
  • 1950-1954  (1)
  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A Sm-poor mixture of Fe-substituted Sm2Co17, having the nominal stoichiometry of Sm0.080Co0.645Fe0.276, was ball-milled to explore the possibility of enhancing its remanence through direct microstructural refinement. With milling, the Sm2(Co0.7Fe0.3)17 compound disassociates to a body-centered-cubic supersaturated SmCoFe solid solution and a residual SmCoFe amorphous phase. Correspondingly, the coercive field values first increase, peaking at 0.83 kOe after 180 min of milling, then decrease with continued milling to 〈0.1 kOe after 1200 min. The remanence, as Mr/Ms, is measured to track closely the coercive field behavior, experiencing modest increases to 0.26 after just 120 min of milling. Magnetization values are found to increase first with the dissociation of the 2:17 phase, and again with the ejection of Sm from the bcc component. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ba-hexaferrite thin films for recording media applications are often fabricated by a two-step process: sputter deposition of an amorphous precursor, followed by annealing to crystallize the BaFe12O19 phase. The magnetic anisotropy of the crystalline films can be either in-plane or perpendicular, depending on the sputtering process used in the first step. However, conventional structural characterization techniques have not been able to distinguish between different as-sputtered films. Using polarization-dependent extended x-ray absorption fine structure (PD-EXAFS), we have observed anisotropic local structure around both Ba and Fe atoms in the amorphous precursor films. Comparison of the results suggests that the amorphous films consist of networks of Fe atoms surrounded by their O nearest neighbors, with Ba atoms fitting into in-between spaces as network modifiers (there might also be some minor Fe network modifying contribution). The local structural anisotropy of the amorphous films appears to determine the orientation of the fast-growing basal plane directions during annealing, and thus the directions of the c axes and the magnetic anisotropy. © 1996 American Institute of Physics.
    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 79 (1996), S. 953-956 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A low pressure metalo-organic chemical vapor deposition (LPMOCVD) technique to form Co2+ and Ce4+ doped yttrium iron garnet (Y3−xCexFe5−xCoxO12: Co,Ce:YIG) films is described. A large concentration of Co2+ doping with x=0.3–0.7 results in uniaxial anisotropy perpendicular to the plane of the film with high coercivity values and sufficiently high saturation magnetization values. This has been possible by an alternate doping scheme where commonly used compensator, Ge4+ at Fe3+ sites has been replaced by a new compensator Ce4+ at Y3+ sites in the Co-doped YIG films. The structural and compositional aspect of stabilized garnet phase in Co2+,Ce4+:YIG thin films and optical, thermomagnetic and magnetic hysteresis properties are presented. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2073-2075 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The evolution of the local atomic environment around Fe atoms in very thin (15 nm), amorphous, partially crystallized and fully crystallized films of Fe80B20 was studied using extended x-ray absorption fine structure (EXAFS) measurements. The relative atomic fraction of each crystalline phase present in the annealed samples was extracted from the Fe EXAFS data by a least-squares fitting procedure, using data collected from t-Fe3B, t-Fe2B, and α-Fe standards. The type and relative fraction of the crystallization products follows the trends previously measured in Fe80B20 melt-spun ribbons, except for the fact that crystallization temperatures are ≈200 K lower than those measured in bulk equivalents. This greatly reduced crystallization temperature may arise from the dominant role of surface nucleation sites in the crystallization of very thin amorphous films. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 943-945 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sidegating in GaAs integrated circuits can be eliminated in molecular beam epitaxially grown structure with the incorporation of a GaAs buffer layer grown at low substrate temperatures (200–300 °C). We have grown two films which were identical except one had the low-temperature buffer layer included in the film structure. The films were modulation-doped heterojunctions designed to produce a high-mobility two-dimensional electron gas. The electrical characteristics of the two-dimensional electron gas were identical for the two samples. No deleterious effect on the mobility or carrier density was observed with the incorporation of the low-temperature buffer layer. At 4.2 K both films exhibited carrier densities of 4×1011 cm−2 and mobilities of (1.4–1.7)×106 cm2/V s in the dark. After a brief illumination at 4.2 K, the samples exhibited carrier densities of 5×1011 cm−2 and mobilities of (1.6–2.0)×106 cm2/V s. These electron mobilities are comparable to the highest electron mobilities ever obtained at these electron densities.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1670-1671 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of heat treatment on the minority-carrier surface recombination velocity in hydrogen-passivated polycrystalline silicon samples has been studied in the temperature range 350–500 °C using the electron-beam-induced current mode of a scanning electron microscope. Minority-carrier trap center densities, calculated from the minority-carrier surface recombination velocity data, varying from 8×1012 to 1.2×1012 cm−2 have been measured. A finite decrease in the minority-carrier trap center density indicates that hydrogen atoms diffuse to the surface from the bulk of the hydrogenated samples. The activation energy of hydrogen diffusion in silicon is found to be 0.53±0.04 eV.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have grown pseudomorphic InxGa1−xAs/In0.52Al0.48As modulation-doped heterostructures by molecular-beam epitaxy under carefully controlled growth conditions. Mobilities as high as 13 900, 74 000, and 134 000 cm2/V s are measured at 300, 77, and 4.2 K in a heterostructure with x=0.65. Shubnikov–de Haas measurements indicate that the change in the effective mass with increasing In is not significant and is not responsible for the enhancement in mobilities. We believe that the improvement results from reduced alloy scattering, reduced intersubband scattering, and reduced impurity scattering, all of which result from a higher conduction-band offset and increased carrier confinement in the two-dimensional electron gas. The high-field electron velocities have been measured in these samples using pulsed current-voltage and pulsed Hall measurements. A monotonic increase in velocities is observed both at 300 and 77 K with an increase of In content in the channel. Velocities of 1.55×107 and 1.87×107 cm/s are measured at 300 and 77 K, respectively, in a In0.65Ga0.35As/In0.52Al0.48As modulation-doped heterostructure.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3778-3778 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Y1.8Er0.2Fe14B is an interesting system in that the tendency of the Er ions to order in the basal plane is almost exactly canceled at low temperatures by the uniaxial anisotropy of the iron sublattice.1 We have performed torque magnetometry measurements in all three principal planes of a single crystal of this material at temperatures from 4 to 300 K in magnetic fields up to 60 kG, which is adequate to produce near saturation even in directions away from the principal axes, thus allowing us to determine the magnetocrystalline anisotropy free energy as a function of orientation and temperature. The free energy data were compared with calculations using the full set of crystal field parameters allowed by symmetry.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3320-3322 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using co-sputtering, 10–300 A(ring) particles of Fe and Co have been prepared in an insulating BN matrix. The Fe particles have the α-Fe structure. The saturation magnetic moment of the iron particles per at. % Fe was found to be approximately independent of the Fe concentration and equal to the value of α-Fe. The system undergoes a metal–nonmetal transition at approximately 40 vol % Fe. For concentrations of Fe particles above this threshold the temperature dependence of the resistivity is metallic and the room-temperature coercivity is large (50–100 Oe). For the Co particles, the room-temperature coercivity is about twice as large as Fe above the metal–nonmetal threshold. Below the metal–nonmetal threshold the particles behave as superparamagnets and the coercivity is approximately zero.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 3550-3552 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A nondestructive method to determine the diffusion length of minority carriers in a p-silicon wafer is outlined. This novel method is based on creating an accumulation layer on one side and an inversion layer on the other side of the wafer by depositing thin semitransparent layers of high (e.g., palladium) and low (e.g., aluminum) workfunction metals, respectively. The wafer acquires a structure akin to p+-p-n+ and is capable of generating a photocurrent when illuminated. The photocurrent Isc (where sc represents short circuit) as a function of the intensity Pin of a monochromatic radiation incident on the accumulation layer (p+) side of the wafer is measured. The diffusion length L is determined from the slope of the Jsc vs Pin curve. The values of L so determined were compared with that determined from the measurement of spectral response by illuminating the wafer from the inversion layer (n+) side and were found to be in excellent agreement.
    Type of Medium: Electronic Resource
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