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  • American Institute of Physics (AIP)  (69)
  • 1990-1994  (69)
  • 1970-1974
  • 1960-1964
  • 1
    Electronic Resource
    Electronic Resource
    A spectrometer for the measurement of reflectance-difference spectra (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2147-2152 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a spectrometer (visible-ultraviolet photon energy range) for the measurement of reflectance-difference spectra of cubic semiconductors. The spectrometer employs a photoelastic modulator to modulate the polarization of the light incident on the sample and allows for a simple procedure to correct the measured spectra for parasitic components associated with such modulation. The instrument reported has a higher throughput than more conventional setups. To illustrate the spectrometer performance we report on reflectance-difference spectra of (001) oriented GaAs single crystals doped with silicon donors at a level of 1018/cm3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143952
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic transitions in Pr2NiO4 single crystal : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6329-6331 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of a stoichiometric Pr2NiO4 single crystal have been examined by means of the temperature dependence of the complex ac susceptibility and the isothermal magnetization in fields up to 200 kOe at T=4.2 K. Three separate phases have been identified and their anisotropic character has been analyzed. A collinear antiferromagnetic phase appears first between TN = 325 K and Tc1 = 115 K, where the Pr ions are polarized by an internal magnetic field. At Tc1 a first modification of the magnetic structure occurs in parallel with a structural phase transition (Bmab to P42/ncm). This magnetic transition has a first-order character and involves both the out-of-plane and the in-plane spin components (magnetic modes gx and gxcyfz, respectively). A second magnetic transition having also a first-order character is also clearly identified at Tc2 = 90 K which corresponds to a spin reorientation process (gxcyfz to cxgyaz magnetic modes). It should be noted as well that the out-of-phase component of χac shows a peak around 30 K which reflects the coexistence of both magnetic configurations in a wide temperature interval. Finally, two field-induced transitions have been observed at 4.2 K when the field is directed along the c axis. We propose that the high-field anomaly arises from a metamagnetic transition of the weak ferromagnetic component, similarly to La2CuO4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349958
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  • 3
    Electronic Resource
    Electronic Resource
    An analysis of the high-temperature relaxation in polycrystalline magnetite : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6100-6102 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic relaxation measurements were performed in the temperature range 200〈T(K)〈800 on vacancy-doped polycrystalline magnetite. Important relaxation peaks have been observed in the temperature ranges 250〈T(K)〈350 (peak III) and 400〈T(K)〈600 (peak I). Particular attention has been focused on the behavior of peak I where isothermal measurements have extended over times up to 105 s. It is argued that the main features of peak I are compatible with a dislocation relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355473
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  • 4
    Electronic Resource
    Electronic Resource
    Evolution of recombination in a solid HDDR processed Nd14Fe79B7 alloy : The 6th joint magnetism and magnetic materials (MMM)−intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6825-6827 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A high-resolution scanning electron microscope was used to study the microstructural changes occurring during the desorption and recombination stages in a cast Nd14Fe79B7 alloy HDDR processed at 780 °C. Phase identification was based on backscattered electron contrast. In the early stages of desorption, the disproportionated structure in the matrix coarsens to produce a mixture of Nd-rich (NdH2 and/or Nd) and Fe-rich (αFe and/or Fe2B) clusters. At the center of the specimen, regions of recombined multicrystalline Nd2Fe14B phase are observed associated with Nd- and Fe-rich clusters. When desorption of hydrogen is almost complete, the microstructure consists of a Nd2Fe14B matrix with a few remaining Nd- and Fe-rich clusters. The subsequent completion of recombination results in a multigrained Nd2Fe14B structure, some grains being separated by Nd-rich material. The magnetic properties of the Nd14Fe79B7 alloy have been measured at significant stages during the desorption/recombination process at 600 °C, the stages being deduced from electrical resistivity measurements. Initially, the material is noncoercive with a high magnetization at 1100 kA/m, reflecting the high proportion of αFe in the sample. As recombination proceeds, the magnetization drops and the coercivity increases as the fine-grained Nd2Fe14B develops and the αFe disappears.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358143
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  • 5
    Electronic Resource
    Electronic Resource
    Large stable second-harmonic coefficients in an azo-dye attached polymer oriented by corona poling (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4273-4275 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Second-harmonic generation and spectroscopic absorption measurements were made over a 15-month period to study the nonlinear-optical thin-film properties of an azo-dye attached polymer in which the dye chromophores were oriented by corona poling. Stable, resonance-enhanced values of the nonlinear optical coefficient d33 for the fundamental of 1.064 μm were as high as 68 pm/V. The stabilized order parameter, calculated from absorbance measurements, was found to be 0.51 for the chromophores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355969
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  • 6
    Electronic Resource
    Electronic Resource
    A study of strain in thin epitaxial films of yttrium silicide on Si(111) (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1517-1520 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of an x-ray diffraction analysis of epitaxial yttrium silicide films grown on Si(111), with thicknesses ranging from 14 to 100 A(ring). The macroscopic strain along the out-of-plane direction for films containing pits or pinholes follows the trend observed previously in films of thicknesses up to 510 A(ring). The out-of-plane lattice parameter decreases linearly with film thickness. We show preliminary evidence that pinhole-free films do not follow the above trend, and that strain in these films has the opposite sign than in films with pinholes. Finally, our results also indicate that the mode of growth, coupled to the interfacial thermal properties of the films, affects the observed value for the strain in the films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356387
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  • 7
    Electronic Resource
    Electronic Resource
    Pseudospectral Møller–Plesset perturbation theory through third order (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 3631-3638 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a formulation and implementation of Møller–Plesset perturbation theory in a pseudospectral framework. At the second-order level, the pseudospectral formulation is a formally a factor of N/n faster than conventional approaches, while the third order is formally faster by a factor of n, where N is the number of atomic orbitals and n is the number of occupied orbitals. The accuracy of the resulting energies is probed for a number of test cases. Practical timings are presented and show conclusively that the pseudospectral formulation is faster than conventional ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466350
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  • 8
    Electronic Resource
    Electronic Resource
    Liquid EXAFS cells for measurements in transmission and fluorescence mode of corrosive samples (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2153-2154 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design of two small, compact and portable cells for EXAFS measurements of liquids is presented. One of the cells has been optimized for transmission measurements and the other for fluorescence. The sample chamber of both cells has been designed metal free to avoid corrosion by acids or bases. Materials and construction of the cell are such that their cost is quite low. The cells have been tested by recording EXAFS spectra of ionic aqueous solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144718
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  • 9
    Electronic Resource
    Electronic Resource
    A coincidence system for studying collisional ion dissociation: Application to H+3 in He (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2939-2940 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple coincidence circuit has been built and attached to conventional pulse counters to obtain the energy distribution of the coincident ion pair arising from the three-body polar dissociation process H+3+He→H++H++H−. The coincidence circuit is based on TTL components and a solid-state delay line. A method to derive the true coincidence H+–H− energy distribution is described, from which properties such as the inelastic energy loss and angle of proton ejection can be obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144581
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  • 10
    Electronic Resource
    Electronic Resource
    Optical interference method to obtain thickness and refractive indices of a uniaxial medium (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2489-2493 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Optical interference fringe measurements of the thickness of weakly absorbing media can be rapid, accurate, and nondestructive. When the refractive index n of the sample is known, it will give us the layer thickness d. If, however, n is unknown, at least two independent spectrophotometric measurements are needed to obtain both n and d. A statistically based scheme is proposed to analyze the interference pattern in order to determine the refractive index and the thickness of the sample. The absolute interference order is also determined with the proposed technique. The major approximation inherent in the method is that the layer must be weakly absorbing and nondispersive over the wavelength region of interest. The method is applied to determine the optical constants of a uniaxial medium with the optical axis parallel to the faces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144707
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