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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6152-6153 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of Dy2Fe17 and Dy2Fe17C have been reported. The expansion of the lattice and increase of Curie temperature Tc and magnetization M have been found for Dy2Fe17C, and compared with Dy2Fe17. From the study of 57Fe Mossbauer spectra, we found that the average hyperfine field of Dy2Fe17C is about 5 T larger than that of Dy2Fe17. The isomer shift of the 4f site is smaller for Dy2Fe17C compared with Dy2Fe17.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2464-2466 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bulk superconductivity with Tc (zero) up to 95 K in a Tl0.5Pb0.5Ca0.9Ce0.1Sr2Cu2 oxide with an Y1Ba2Cu3Oy -like structure was observed. Single-phase samples, tetragonal in structure with a=0.380±0.001, c=1.195±0.001 nm, and of P4/mmm space group, were prepared. The results represent the first case where Ce substitution significantly raised the Tc of a known compound. The samples were remarkably homogeneous both in composition and structure. The compounds were highly reproducible and stable. The preparative conditions were found to be much less stringent than those of other copper-based high Tc superconductors.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 913-915 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystal structure and microstructures of a high Tc BiSrCaCuO (BSCCO) compound were characterized by transmission electron microscopy, x-ray diffraction (XRD), and energy dispersive spectrometry (EDS). Convergent beam electron diffraction (CBED) analysis established that the crystal is of mm2 symmetry. Combined with electron diffraction, XRD, and EDS data, the high Tc superconducting BSCCO compound was found to be of the Pnn2 space group, orthorhombic in structure with a=0.540 nm, b=2.689 nm, and c=3.040 nm and with an approximate composition of Bi2Sr2CaCu2Oy. Diffraction contrast analysis indicated that the dislocations are predominantly of screw character with [010] or [001] Burgers vectors. However, edge type dislocations and dislocations with [100] Burgers vector were also observed. The magnitude of the Burgers vector along the [100] direction was determined to be 1/2 [100] by high-resolution lattice imaging. Stacking faults and small-angle grain boundaries were frequently observed. The presence of a high density of defects in the superconducting oxide may facilitate the processing of the material and serve as effective flux line barriers.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2142-2144 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Direct conversion of superconducting Y2Ba4Cu7O15−δ (Y-247) from YBa2Cu3O7−x (Y-123) was achieved at atmospheric pressure. The Y-247 samples were synthesized by the reactions of Y-123 and Cu-(NO3)2 at 860 °C in an O2 ambient. The results strongly suggest that Y-247 is a thermodynamically more stable phase than Y-123 at the atmospheric pressure. The conversion also provides a novel and simple route to synthesize the Y-247 compound.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2029-2031 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the resistivity, structural, and magnetic susceptibility measurements for Tl0.5Pb0.5(Ca1−xMx)Sr2Cu2Oy superconductors with M equal to the natural mixture of rare-earth elements and x=0, 0.05, 0.1, 0.2, and 0.3, respectively. The powder x-ray diffraction profile indicates a single-phase, P4/mmm tetragonal crystal structure with a=0.380±0.002 nm and c=1.205±0.002 nm for a Tl0.5Pb0.5(Ca0.9M0.1)Sr2Cu2Oy superconductor. Tc (zero)'s were found to be 79, 91, 101, 97, and 87 K for x=0, 0.05, 0.1, 0.2, and 0.3, respectively. Hc1 of Tl0.5Pb0.5(Ca0.9M0.1)Sr2Cu2Oy was estimated to be around 1.8 kG at 5 K, and Jc about 1.35×103 A/cm2 with a 20 kG applied field at 5 K. The Meissner signal of this sample indicates the Tc onset ∼100 K, and the mass diamagnetic susceptibility −χg at 5 K is 2.52×10−3 cm3/g (field cooled at 100 G).
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1434-1436 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystal structure of a Tl-Ca-Ba-Cu-O compound in Tc onset=155 K and Tc zero=123 K superconducting specimens was characterized by transmission electron microscopy. Convergent beam electron diffraction analysis established that the phase is of P4/mcc space group. The lattice parameters of the phase were determined to be a=b=0.394 nm and c=3.95 nm. The phase was found to be primarily of a ten-subcell structure by both high-resolution lattice imaging and diffraction pattern analysis. The composition of the grains with the ten-subcell structure being predominant was measured by energy dispersive spectrometry to be TlCa2Ba3Cu4Ox. Polytypes of the phase with four- and five-subcell structures were also observed. The five-subcell structure was identified to be of P4/mmm space group with a=b=0.394 nm and c=1.97 nm. The compositions of the specimens were measured to vary in composition ratios of Tl, Ca, Ba, and Cu from 1:2:2:3 to 1:2:3:4. The results strongly suggested that the TlCa2Ba3Cu4Ox phase is a high Tc superconducting phase with an exciting possibility that superconducting transition occurs at 155 K for this phase.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1071-1073 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A gallium arsenide film is grown embedded in masked pre-etched wells in silicon vicinal (001) substrates by molecular beam epitaxy. The morphology and crystallinity of the embedded GaAs on Si layers are identical to those of large area GaAs on Si grown on the same wafer, as indicated by the comparison of Nomarski contrast photomicrographs and electron channeling patterns. High-resolution electron microscope images reveal the epitaxial relation of the GaAs/Si interface on the bottom and the sidewall of the wells. On the slope most of the dislocations are restricted to a narrow region near the interface. The same photoluminescent behavior is found for the GaAs deposit in the different silicon environments. This embedded growth technique is suitable for realization of a coplanar GaAs on Si surface.
    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 64 (1988), S. 3593-3597 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscopy (TEM), energy dispersive analysis of x ray (EDS), x-ray diffraction, electrical resistance, and magnetic susceptibility measurements were applied to characterize the structure and microstructures of a high-Tc superconducting YBaSrCu3O7−δ compound. The sintered samples were found to be predominantly of a single phase with a modified perovskite structure. Combined EDS/TEM and high-resolution lattice imaging with computed image simulation data showed that the atomic ratio of Sr and Ba atoms is about unity and Ba sites in YBa2Cu3O7−δ compound were partially substituted by Sr atoms in the three-layer perovskite structure, in agreement with the results of a previous neutron diffraction study. It was also found that the marked contrast difference in high-resolution images along [100] and [010] directions of the high-Tc oxygen-deficient superconducting crystals can be used to advantage to distinguish [100] and [010] directions of the modified perovskite structure in TEM. Lattice defects such as twins and dislocations were observed and analyzed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1650-1652 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tetragonal LaCo13−xSix compounds have been obtained by annealing cubic LaCo13−xSix compounds. The space group for the tetragonal structure is I4/mcm. Atomic ordering occurs in the tetragonal LaCo13−xSix compounds, i.e., Si atoms show a strong preference for occupying a specific crystallographic position. The tetragonal LaCo13−xSix compounds are ferromagnetic with Curie temperatures higher than 900 K. The magnetic moment per Co atom in the tetragonal LaCo13−xSix compounds decreases with Si content, which can be explained by the rigid-band model. The tetragonal LaCo13−xSix compounds are expected to be promising candidates for permanent magnets purpose.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1224-1226 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Autocorrelation function (ACF) analysis has been applied to the high resolution transmission electron microscope images of amorphous interlayers formed in the interfacial reactions of ultrahigh vacuum deposited molybdenum thin films on (111)Si. Mo3Si was identified to be the first nucleated crystalline phase which is correlated to the stable structure of the amorphous Mo-Si alloy. Both Mo3Si and Mo5Si3 were found to form simultaneously under certain annealing conditions. The results demonstrate the usefulness of the ACF analysis of atomic images in amorphous interlayers formed in the initial stage of reactions in metal thin films on silicon.
    Type of Medium: Electronic Resource
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