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  • 1
    Electronic Resource
    Electronic Resource
    Wet-process preparation of amorphous Y-Fe oxide films ferromagnetic at room temperature : 38th Annual Confrerence on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6094-6096 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Yttrium iron ferrite films of amorphous structure (as examined by x-ray diffraction), having ferromagnetic moment at room temperature, are successfully synthesized from an aqueous solution by a ferrite plating method in which the substrate is heated by Xe-lamp beams. The atomic ratio of Y/Fe in the films is adjusted to Y/Fe=0.6, as in Y3Fe5O12, by properly choosing the atomic ratio (Y/Fe=3.5) in the reaction solution. The magnetization of the films at room temperature is 10–40 emu/cc, several times smaller than that observed for crystalline YIG. It exhibited, however, a paramagnetic Mössbauer spectrum at room temperature, suggesting that the weak magnetization is ascribed to the magnetic impurity phase whose concentration is too small to be discerned by x-ray diffraction and Mössbauer measurements. The spectrum has an isomer shift of 0.22 mm/sec at 300 K and a hyperfine field splitting of 462 kOe at 12 K, indicating that the Fe ions are in a trivalent high spin state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355471
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  • 2
    Electronic Resource
    Electronic Resource
    Cation distribution in NiZn-ferrite films determined using x-ray absorption fine structure : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4561-4563 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have applied extended x-ray absorption fine structure (EXAFS) spectroscopy to study the cation distribution in a series of spin-sprayed NiZn-ferrite films, Ni0.15ZnyFe2.85−yO4 (y=0.16, 0.23, 0.40, 0.60). The Ni, Zn, and Fe EXAFS were collected from each sample and analyzed to Fourier transforms. Samples of Ni-ferrite, Zn-ferrite, and magnetite were similarly studied as empirical standards. These standards, together with EXAFS data generated from the theoretical EXAFS FEFF codes, allowed the correlation of features in the Fourier transforms with specific lattice sites in the spinel unit cell. We find that the Ni ions reside mostly on the octahedral (B) sites whereas the Zn ions are predominantly on the tetrahedral (A) sites. The Fe ions reside on both A and B sites in a ratio determined by the ratio of Zn/Fe. The addition of Zn displaces a larger fraction of Fe cations onto the B sites serving to increase the net magnetization. The fraction of A site Ni ions is measured to increase peaking at ≈25% for y=0.6. At higher Zn concentrations (y≥0.5) the lattice experiences local distortions around the Zn sites causing a decrease in the superexchange resulting in a decrease in the net magnetization. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361725
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  • 3
    Electronic Resource
    Electronic Resource
    Aging of the dielectric and piezoelectric properties of relaxor ferroelectric lead magnesium niobate–lead titanate in the electric field biased state (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3181-3187 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The aging characteristics of the electrostrictive lead magnesium niobate–lead titanate [(1−x)PMN–xPT] under dc bias field were investigated. It was observed that the amount of aging increases with the PT content for the compositions investigated (x≤0.3). For a fixed composition, the aging rate rises with temperature. It was shown that the aging follows a stretched exponential time law, which is typical for the time-dependent behavior in polar glass and random field systems. In PMN–PT, the dielectric constant shows a much weaker aging than the piezoelectric coefficient, reflecting the importance of the stress coupling of the defect field to the micropolar region during the aging since the polar vector of the microregions can have both 180° and non-180° reorientations while only the non-180° reorientation contributes to the observed piezoelectric effect. Experimental results also reveal that the defect field developed during the aging in these materials under dc bias field is quite different from those in normal ferroelectrics and in Mn-doped PMN and 0.9 PMN–0.1PT. The direction of the defect electric field is opposite to the direction of the original dc bias field, indicating that the defect field is the result of a direct coupling to the external bias field rather than induced by the polar domains. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361261
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  • 4
    Electronic Resource
    Electronic Resource
    Study of band-gap narrowing effect and nonradiative recombination centers for heavily C-doped GaAs by photoluminescence spectroscopy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4822-4824 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The band-gap narrowing effect of GaAs as a function of carbon doping concentration has been measured using photoluminescence (PL) spectroscopy on samples grown by metalorganic chemical-vapor deposition. The range of carbon concentration varies from 3.4×1018 to 1.1×1020 cm−3. The experimental results obtained from PL spectra taking tailing effects into account are in good agreement with recent theoretical calculations. The intensity of PL spectra decreases rapidly when the free-carrier concentration is higher than about 4×1019 cm−3. This phenomenon cannot be explained with only the varying tendency of the minority-electron lifetime of the radiative recombination process, indicating the introduction of additional nonradiative recombination centers in heavily C-doped GaAs. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359406
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  • 5
    Electronic Resource
    Electronic Resource
    Local structure of porous silicon (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5171-5178 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Local structural information has been obtained from extended x-ray-absorption fine-structure measurements on samples of porous silicon produced under various conditions, and these have been correlated with photoluminescence emission and excitation spectra. The x-ray near-edge structure (XANES) shows the existence of a feature in between those assigned to Si—Si and Si—O bonding. Laser-induced mass analysis indicates that the presence of various silicon hydroxides correlates strongly with the strength of this peak. In addition, although porous silicon consists of a surface whose roughness is of the order of nm, it has been possible to obtain depth-profiling reflected x-ray-absorption fine structure (REFLEXAFS) and reflectivity from some samples. The REFLEXAFS XANES again shows the additional feature, the strength of which increases with the intensity of the Si-Si peak, that is, with depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357234
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  • 6
    Electronic Resource
    Electronic Resource
    An experimental investigation of electromechanical responses in a polyurethane elastomer (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2770-2776 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electromechanical response of a polyurethane elastomer was investigated at room temperature and in the temperature range near its glass transition. It was found that the Maxwell stress contribution to the strain response can be significant at temperatures higher than the glass transition temperature. In addition, the material exhibits a very high electrostrictive coefficient Q, about two orders of magnitude higher than that of polyvinylidene fluoride. It was also found that in a polymeric material, the chain segment motions can be divided into those related to the polarization response and those related to the mechanical response and the overlap between the two yields the electromechanical response of the material. In general, the activation energies for different types of motion can be different, resulting in different relaxation times in the dielectric, the elastic compliance, and the electrostrictive data, as observed in the polyurethane elastomer investigated. The experimental results indicate that at the temperatures investigated, the activation energy for the mechanical related segment motions is higher than that of nonmechanical related segment motions. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363981
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  • 7
    Electronic Resource
    Electronic Resource
    Reflection of plane waves at medium–composite interfaces and input acoustic impedance of laminated piezoceramic polymer composites (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5503-5505 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plane wave propagation at the composite–medium interface is analyzed for the piezoceramic polymer composites with laminated periodic structure. It is found that the input acoustic impedance of the composite depends on the elastic properties of the medium at the interface and in general is a complex number and dispersive. It is also found that the reflected wave from the medium–composite interface suffers a more than 180° phase change, which implies that the thickness of the conventional antireflection "quarter wave matching layer'' at the interface should be less than a quarter wave length. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362741
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  • 8
    Electronic Resource
    Electronic Resource
    Characteristics of the electromechanical response and polarization of electric field biased ferroelectrics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2549-2555 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electromechanical and dielectric responses of ferroelectric materials near paraelectric–ferroelectric (PF) phase transitions are examined both experimentally and theoretically. It is shown that the type of PF transition, i.e., first order and continuous transitions, and diffused phase transition found in relaxor ferroelectrics, has marked effect on the electromechanical and dielectric response behavior for materials under electric field bias. It is demonstrated that an exceptionally large piezoelectric and electromechanical response can be achieved in materials with a first order PF transition. For example, in Ba1−xSrxTiO3 (x∼0.35) ceramics at room temperature, a piezoelectric d33 larger than 1500 pm/V with very little frequency dispersion can be obtained. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358785
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  • 9
    Electronic Resource
    Electronic Resource
    Dynamic modeling of piezoceramic polymer composite with 2-2 connectivity (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6014-6016 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A dynamic theory on the piezoceramic polymer composite with 2-2 connectivity is presented. By adopting an approach similar to the Lamb waves in a plate, the distributions of the elastic and electric fields in a piezocomposite are solved and the dispersion curves are obtained. Based on these results, a method is developed to evaluate the sound velocity, acoustic impedance, and electromechanical coupling factor kt in a composite. The theoretical predictions are in excellent agreement with the experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358354
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  • 10
    Electronic Resource
    Electronic Resource
    High-frequency strain response in ferroelectrics and its measurement using a modified Mach-Zehnder interferometer (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2807-2813 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we report on a modified Mach-Zehnder interferometer which is capable of measuring the ultrashort time strain response of a sample. Using this instrument, the dispersion of piezoelectric and electrostrictive coefficients of several commonly used ferroelectrics was measured. The strain switching behavior of lead lanthanum zirconate titanate (PLZT) 9/65/35 driven by a square pulse electric field was studied. The results show that the switching rise time of the strain response for PLZT 9/65/35 can be much shorter than 5 μs at a pulse field strength near 25 kV/cm and that the fall time of the strain response is considerably shorter than the rise time in the experimental field strength range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342744
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