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  • 1
    Electronic Resource
    Electronic Resource
    Observation of multiple step de-excitation in luminescent single conjugated polymers (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 3848-3852 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The fluorescence intensity fluctuation and polarization modulation of spin-cast single fluorescent conjugated polymers of 2,5-dioctyloxy p-phenylene vinylene (DOO-PPV) with length of the order of the persistence length have been studied. The results indicate that this type of polymer behaves like a collection of semi-independent excitons, with dipoles aligned predominately in the same direction. This suggests that this type of polymer can be considered as a linearly extended rigid structure (i.e., a straight rod). The fluorescent transient exhibits a multiple-step-like behavior with the count rate at each step being a multiple of a common step-size. The fluorescence variation follows the excitation polarization with a DC background observable in some molecules. This DC background indicates that the chromophores in some polymers are not aligned in the same direction. Variations in the Huang–Rhys factor at a single polymer level are also observed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1343874
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  • 2
    Electronic Resource
    Electronic Resource
    Studies of magnetic interactions between Gd granules in copper matrix : 38th Annual Conference ion Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6616-6618 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrafine Gd particles in the Cu metallic material have been obtained by rapid annealing of sputtered metastable GdxCu1−x alloys. The particle shape and size were measured by a transmission electron microscopy. The evolution of crystal structure with annealing temperature has been investigated by x-ray diffraction and electron diffraction. It has been found that the Gd granules have formed following annealing above 300 °C and the granular size increases with rising annealing temperature. The magnetic data show that the as-sputtered metastable Gd0.1Cu0.9 and Gd0.2Cu0.8 alloys obey a Curie–Weiss law at high temperature with a negative value of θ. After annealing, the θ value varies with annealing temperature according to an oscillatory function. The evolution of the magnetic properties and microstructure during annealing are described in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356916
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  • 3
    Electronic Resource
    Electronic Resource
    Improved thermal stability of Mo-modified γ-Fe2O3 particles (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5152-5154 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Acicular α-(FeO)OH particles were synthesized using the chemical coprecipitation method with the reaction system of Fe2Cl2-NaOH. The Mo-modified γ-Fe2O3 particles are obtained by adding the proper amount of sodium molybdate to the solution of geothite, followed by the processes of dehydration, reduction, and oxidation. The thermal stability was investigated by thermal differential analysis. It was found that the transition temperature of γ-Fe2O3→α-Fe2O3 increases from 544 °C for the unmodified particles to 720 °C for particles containing 4% by weight of molybdenum. The improved thermal stability has the advantage that the temperature for the oxidation of Fe3O4 particles can be considerably increased without the risk of forming nonmagnetic α-Fe2O3 particles. The magnetization (σs) and coercivity (Hc) of the magnetic acicular γ-Fe2O3 have been determined from room temperature to 200 °C with a vibrating sample magnetometer. The results indicate that both σs and Hc at room temperature decrease with increasing Mo content. The dependence of Hc can be approximately described by the linear equation Hc=Hc,0(1−AT) over that temperature range. The temperature coefficient A decreases with Mo content until the Mo content reaches 4 wt. %. The origin of improved thermal stability is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344646
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  • 4
    Electronic Resource
    Electronic Resource
    Structural and magnetic studies of metastable Gd–Cr alloys over the entire composition range : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6308-6310 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Under equilibrium conditions, Gd and Cr are immiscible. However, by vapor quenching using sputtering techniques, metastable GdxCr1−x alloys can be prepared over the entire composition range. Since pure Gd and Cr are ferromagnetic and antiferromagnetic, respectively, such metastable alloys reveal the evolution from ferromagnetic ordering to antiferromagnetic ordering. X-ray diffraction shows that the structure for samples with x〈0.20 is body-centered-cubic, the same as that of Cr, whereas for x(approximately-greater-than)0.20 it is hexagonal-close-packed (hcp), as is Gd. Surprisingly, no single phase amorphous state has been found. Pure Gd is ferromagnetic with Tc near room temperature. With the addition of Cr, Tc decreases slowly to about 226 K at x=0.60, and decreases rapidly as the Gd concentration is further reduced. For samples with x〈0.50, magnetization at 5 K cannot be saturated even in an external field of 50 kOe, due to competing ferromagnetic and antiferromagnetic interactions. A magnetic phase diagram has been determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349977
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  • 5
    Electronic Resource
    Electronic Resource
    Surface modification and patterning of conjugated polymers with near-field optical microscopyWe would like to acknowledge Dr. Y. Chiu, Dr. M. Hayashi And Professor J. Hsu for the critical reading of the manuscript. This Research was funded by the National Science Council, Taiwan (ROC). (1996)
    Weinheim : Wiley-Blackwell
    Advanced Materials 8 (1996), S. 573-576 
    Details
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19960080708
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  • 6
    Electronic Resource
    Electronic Resource
    Structural and Mössbauer studies of Fe1−xAlx alloys over the entire composition range (1992)
    Springer
    Hyperfine interactions 69 (1992), S. 451-454 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Metastable Fe1−xAlx alloys over the entire composition range have been investigated by X-ray diffraction and Mössbauer effect measurements. Alloys with x less than 0.55 are bec, whereas those with x〉0.9 are fce, in between, the samples are amorphous. The Mössbauer spectra at 300 K for the bce alloys with x〈0.5 consist of a broadened sextet and the spectra for the alloys with x≥0.5 are quadrupole-split doublets with a slight asymmetry. The magnetic hyperfine field at 4.2 K decreases monotonically with Al concentration from 340 kOe in pure Fe to zero at x=0.7. The isomer shift increases essentially linearly with Al concentration, and reaches a maximum at x=0.75. It is noted that at the boundary of x=0.55 separating the bce and the amorphous states, there is no discernible change in elther hyperfine field or lsomer shift.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02401862
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