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  • 1
    Electronic Resource
    Electronic Resource
    The origin of hard magnetic properties in rapidly quenched Nd4Fe77.5B18.5 alloy : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6980-6982 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Until now, the origin of hard magnetic properties of rapidly quenched Nd-Fe-B alloys with lower Nd concentration is not clear. In this paper, the phase compositions of rapidly quenched Nd4Fe77.5B18.5 alloys annealed under different conditions have been studied by using zero-field spin-echo nuclear magnetic resonance (NMR) and Mössbauer effect (ME) techniques. It is found that there exists a certain amount of Nd2Fe14B phase in the samples annealed at 960 °C and ingot alloy, which have poor hard magnetic properties; while, the sample annealed under optimal condition consists only of bct-Fe3B as the main phase and a small amount of a-Fe. However, the ME result indicates that about 5 at. % Fe atoms in FeIII (8 g) site of bct-Fe3B have been replaced by Nd atoms; the NMR result demonstrates that 11B NMR spectrum is the characteristic peak of bct-Fe3B, but it broadens asymmetrically to the high frequency side, which is due to the bct-Fe3B influenced by Nd atoms. The amplitude of radio frequency (rf) excitation field required to get the maximum 11B spin-echo signal from bct-Fe3B in the sample annealed at 839 °C is only about one third as much as that required to excite the 11B in the bct-Fe3B influenced by Nd atoms in the sample annealed at 670 °C for a short time, which implies the latter has a larger coercivity field than the former. It is concluded that the origin of hard magnetic properties of Nd4Fe77.5B18.5 alloy is not related to the 2:14:1 phase, but to the change of bct-Fe3B itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352404
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  • 2
    Electronic Resource
    Electronic Resource
    NMR study of the short range order in Fe–B amorphous powders prepared by borohydride reduction : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6983-6985 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Fe–B amorphous alloys powders with high boron concentration can be prepared by borohydride reduction (BHR). By adjusting technological factors, the Fe100−xBx amorphous powders with compositions ranging from x=17 to 40 can be easily obtained, but it is difficult to make the amorphous ribbons with such a high B concentration by using rapidly quenched technique, which can usually obtain the amorphous ribbons with the compositions ranging from x=12 to 25. Up to now, there are different points of view about if the short range order (SRO) in the Fe–B amorphous powders prepared by the BHR around room temperature is the same with that in the amorphous ribbons made by rapidly quenched and vapor depositing techniques. In this paper, the SRO in Fe100−xBx amorphous powders with various boron concentration prepared by the BHR have been studied by the zero field spin echo nuclear magnetic resonance (NMR) technique. It was shown that the types of SRO in these samples vary with the B concentration. There exist Fe3B- and Fe2B-like SRO and a small amount of α-Fe in the samples with lower B concentration, while there are Fe3B- and FeB-like SRO in the alloys with higher B concentration. Fe3B-like SRO, however, only exists in the amorphous ribbons obtained by rapidly quenched method. It can be concluded that there are different types of SRO in the amorphous alloys prepared by different methods. This conclusion can explain the reason why the average hyperfine field at Fe sites deceases with the B concentration increasing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352405
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of Ga substitution on the Sm sublattice anisotropy in Sm2Fe17−xGax (0≤x≤8) (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4663-4665 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to study the unique behavior of the Sm sublattice anisotropy, magnetization curves along both the easy and hard directions were obtained at 10 K for Sm2Fe17−xGax (0≤x≤8) powders which were aligned using either static- or dynamic-field alignment methods. The Fe sublattice contribution was isolated by making similar measurements on Y2Fe17−xGax (0≤x≤8), as the presence of Y eliminates the rare-earth sublattice contribution. The results show that the Sm sublattice anisotropy is dominant for x≥1. It increases with increasing Ga content, reaching a (broad) maximum of 1.8×107 erg/cm3 for x(approximate)2–3, and then decreases and becomes negative for x(approximate)5.5. This work shows that the unique behavior of the magneto-crystalline anisotropy for Sm2Fe17−xGax arises from the variation of the Sm-sublattice contribution with Ga substitution. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370440
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  • 4
    Electronic Resource
    Electronic Resource
    Study of the nitrogen diffusion mechanism in R2Fe17 : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4596-4598 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Previously, nuclear magnetic resonance experiments and diffusion calculations have indicated that the distribution of nitrogen atoms in a Y2Fe17Nx particle with intermediate N content is characterized by a nitrided region and an unnitrided region. In order to directly detect this two-region configuration, x-ray diffraction experiments have been carried out on systematically ground nitrogenated samples. Furthermore, x-ray diffraction and 89Y nuclear magnetic resonance on vacuum-annealed samples show that the two-region configuration is stable, and that the nitrogen atoms do not diffuse further into the particle. Thermal conductivity detection measurements indicate that only 5% of the inserted N atoms can be released by vacuum annealing at the nitrogenation temperature. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361738
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  • 5
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance study of the magnetic behavior of ultrafine Co clusters in zeolite NaY : 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. 6576-6578 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 59Co spin-echo nuclear magnetic resonance (NMR) experiments have been carried out at 1.3 and 4.2 K, for external magnetic fields up to 9 kOe, in order to study 6–10 A(ring), single-domain Co clusters isolated inside zeolite NaY supercages. The magnetic behavior is characterized by a superparamagnetic blocking temperature, relaxation time behavior for increasing and decreasing fields, and a dependence on the magnetic history. The observed NMR spectra are broad with structural features characteristic of both fcc- and hcp-like short-range order. Unlike bulk materials, the application of fields up to 9 kOe causes a dramatic increase in the signal intensity. The results are discussed in terms of the particle-size distribution and crystalline anisotropy, and their relationship to the temperature and field dependence of the superparamagnetic/ferromagnetic behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358198
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  • 6
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance study of R2Fe17 (R=Y, Sm, and Gd) hydrides : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5530-5532 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to study the location of hydrogen atoms and the effects of their insertion into R2Fe17, spin–echo NMR experiments have been carried out on the hexagonal Y2Fe17Hx (x=0, 3.0, 4.7), rhombohedral Sm2Fe17Hx (x=0, 1.7, 5.7), and mixed-phase Gd2Fe17Hx (x=0, 2.3, 5.8) compounds. 1H and 89Y spectra obtained from Y2Fe17Hx clearly demonstrate that the hydrogenation process is reversible upon vacuum annealing. For both Y2Fe17Hx and Sm2Fe17Hx, the 1H spectra show two broad peaks; the peaks are tentatively assigned to H atoms in the tetrahedral and octahedral interstitial sites, and a hydrogen filling scheme is proposed. For Gd2Fe17Hx, a single broad 1H peak near 70 MHz is observed; application of an external magnetic field indicates that the hyperfine field has the same direction as the net magnetization. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361842
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  • 7
    Electronic Resource
    Electronic Resource
    Specific Fe site moment enhancement in Y2Fe17 upon N insertion : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4566-4568 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to gain information concerning the separate effects of lattice expansion and Fe–N chemical bonding on the Fe moment for each individual Fe site in R2Fe17Nx systems (R=rare earth), x-ray diffraction, magnetization, and 57Fe nuclear magnetic resonance experiments were carried out on rhombohedral Y2Fe17Nx with N content 0≤x≤2.8. The increase of the average 57Fe hyperfine field (HF) from the unnitrided to the nitrided phase follows the increase in the saturation magnetization, providing evidence that the 57Fe HF does scale with the Fe moment in this system. The changes of the 57Fe HF are not the same for the various Fe sites; e.g., the HF at the 18f site, which has one N atom as a nearest neighbor, has much less enhancement than that at the 9d site, which has no N atoms as a nearest neighbor. More significantly, for the Fe 6c site, the HF does not change at all with nitrogen content. These results are analyzed in conjunction with existing neutron diffraction data regarding the Fe–Fe distance variations upon nitrogenation and yield a very consistent picture. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365429
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  • 8
    Electronic Resource
    Electronic Resource
    Three dimensional alignment of magnetic particles : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5647-5649 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, novel magnetic particle alignment methods, which we refer to as dynamic alignment, are presented. In the process of a dynamic alignment, the magnetic field direction is periodically changed while the particle orientation is captured in epoxy resin. Depending on the manner of the variation of the magnetic field, particles can be aligned in various patterns. By employing the dynamic alignment methods described in this article, the alignment of magnetic particles can be achieved such that particles are aligned along all three crystalline axes. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364683
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  • 9
    Electronic Resource
    Electronic Resource
    Novel main-chain poly-carbazoles as hole and electron transport materials in polymer light-emitting diodes (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1921-1923 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the use of substituted main-chain poly-carbazoles as hole and electron transporting polymers for electroluminescence (EL) applications. The polymers are soluble in common organic solvents and high quality thin films are obtained by spin coating method. A single layer of hole or electron transfer devices with indium tin oxide anode and aluminum cathode shows current densities up to 40–50 mA/cm2, respectively, but no visible emission from either layer. Double-layer structures combining the hole and electron transfer polymers show strong emission originated from the electron transfer layer. The peak of double-layer EL spectrum is about 30 nm redshifted to the peak of corresponding photoluminescence spectrum, which may be due to the formation of an exciplex between the two layers. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119981
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  • 10
    Electronic Resource
    Electronic Resource
    X-ray diffraction and nuclear magnetic resonance studies of Y2Fe17 (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3194-3196 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray structure analysis and 89Y nuclear magnetic resonance (NMR) measurements are presented for the hexagonal and rhombohedral phases of Y2Fe17. The rhombohedral structure has one Y site (designated 6c) and the hexagonal structure has two Y sites (designated 2b and 2d). By combining the x-ray and NMR results, the hyperfine fields corresponding to the three Y sites in these two phases are obtained. Furthermore, a deconvolution of the NMR spectrum for 89Y in the hexagonal Y2Fe17 phase shows that a disordering exists, resulting in an occupancy for the Y 2b sites of approximately 71%. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117958
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