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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is reported that Nd-Fe-B magnetic powders prepared by utilizing the HDDR (hydrogenation, disproportionation, desorption, and recombination) phenomena exhibit high coercivity, and the addition of Co, Ga, and Zr induces magnetic anisotropy in these powders. HDDR phenomena are caused by the heat treatment in hydrogen (H treatment) and subsequently in vacuum (V treatment). Present works describe the effects of V-treatment conditions on magnetic properties of Nd12.6Febal.CoxB6.0 (x=0–17.4) alloys. The powders V-treated at lower temperature show lower remanence and no noticeable magnetic anisotropy. V treatment at higher temperature enhances remanence and increases the differences of remanence between the powders aligned with and without magnetic field. Higher values are obtained in Co added alloys. This result suggests that a selective grain growth of Nd2Fe14B grains during V treatment plays an important role for the inducement of magnetic anisotropy in HDDR-treated powders. The temperature for complete recombination reaction under evacuating condition decreases with increasing Co content. It can be said that Co addition enhances recombination reaction and results in acceleration of grain growth.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5287-5292 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic measurements have been performed on silver clad Tl-1223 and Tl-2223 tapes and a Tl-1223 single crystal to study the critical current properties of these samples. The Tl-1223 tape is shown by both magnetic and transport experiments to exhibit a highly granular nature, much more severe than that seen in the Tl-2223 tape, and in Bi-2223 tapes fabricated by similar rolling and pressing techniques. This characteristic is explained in terms of the poor grain alignment in the Tl-1223 tape resulting from the spherical morphology of Tl-1223 powders, in contrast with the micaceous and easily aligned Bi-2223 and Bi-2212 materials. However, evidence of a small number of strong intergrain links which remain superconducting at 77 K and 8 T is clear. The Tl-1223 single crystal exhibits clear anisotropic behavior, and this, together with the lack of good crystallographic alignment in the tapes is used to explain the variations in irreversibility line behavior between sample forms. The ratio of the irreversibility fields measured with field parallel and perpendicular to the ab plane is approximately 8. A clear "fish tail'' feature is also observed in magnetic hysteresis curves obtained from the Tl-1223 single crystal. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 716-718 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The semiconductor industry is growing rapidly and requires high technologies for nano-structure devices. Ion sources for manufacturing the next-generation semiconductor devices have been studied from the viewpoint of applications to material processing, such as ion beam assisted deposition, ion beam etching, and ion implantation. Recently, large-area ion sources which extract broad ion beams with multiapertures have come to be required not only for processing the size-growing wafers but also for industrial applications to nonsemiconductor materials. However, the uniformity of plasma density over the multiaperture electrodes has not met the requirements yet. We suggest a new method to improve the uniformity by superposing microwaves to an inductively coupled plasma source. Distributions of ion species in the plasma are measured with a quadrupole mass spectrometer which can be moved in vacuum perpendicularly to the beam extraction. The distributions of both plasma density and ion species in the source plasma as well as their properties over a large area are being studied and discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5732-5734 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fe-Cr-Co magnets with radial anisotropy were developed by rotating samples in a magnetic aging furnace. The anisotropy is altered by the applied magnetic field strength. The Fe-25 wt. %Cr-12 wt. %Co-0.5 wt. %Ti alloy aged in a magnetic field of 100 Oe yields the magnetic properties of (BH)max=24 kJ m−3 (3 MGOe) and iHc=48 kA m−1 (600 Oe) parallel to radial direction, which are higher than those of (BH)max=7 kJ m−3 (0.9 MGOe), iHc=33 kA m−1, measured parallel to the circumferential direction. The increment of the applied magnetic field over 200 Oe alters the radial anisotropy into a circumferential one. Microstructural studies indicate that the iron-rich phase is elongated parallel to the direction of induced anisotropy. Computations of the magnetic flux distribution in disk samples confirm the experimental observations.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3707-3709 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Present works describe the development of Fe-Cr-Co-Mo alloys with favorable {110}〈100〉 texture, which will lie along the transverse direction (TD) of the rolled strips. The studied alloy composition is Fe-30 wt. % Cr-15 wt. %Co-3 wt. % Mo-0.1 wt. % Mn-0.05 wt. % S. The magnetic properties of the alloys have been enhanced along the TD and the best magnetic properties obtained with TD alloys are Br=1.2 T (12.0 kG), iHc=82 kA m−1 (1025 Oe), and BHmax=56 kJ m−3 (7.0 MGOe). The favorable texture is developed by secondary recrystallization, caused by a mixture of rolling and annealing. It can be considered that the process adopted in this investigation is useful for mass production of Fe-Cr-Co alloys with high energy products, without forming a columnar structure or a single crystal.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6477-6479 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of composition and additives on the microstructures and magnetic properties of Nd-Fe-B melt-spun ribbons were studied. Experimental results have revealed that homogeneous grain structure with fine grain size was obtained on composition close to 2-14-1 stoichiometry with additives. It was also found that Nb was very effective in increasing both remanence and coercivity in a Nd-Fe-B melt-spun ribbon. A high-energy product of 151.2 kJ/m3 (19.0 MGOe) was obtained from an isotropic (Nd0.5Pr0.5)12Fe72Co8B6Nb2 melt-spun ribbon with a remanence of 0.926 T and a coercivity exceeding 1200 kA/m (∼15 kOe).
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 713-715 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Microwave ion sources have many advantages over dc-discharge ion sources, such as long lifetime and high current for most ion species. But B+ ion current has been the only disadvantage. Here we experimentally study how to get higher B+ ion current by optimizing the shape and volume of the source chamber as well as by increasing the secondary electron emissivity of the chamber wall. We carry out the experiment with regard to the maximum ion beam, lifetime, and dynamic range of the beam current for various ion species. Then, we compare the data with those of the Bernas-type ion source that has been widely used in semiconductor manufacturing factories. As a result of the improvement, the performance of all the above-mentioned aspects of the microwave ion source exceed those of the Bernas-type ion source. © 2000 American Institute of Physics.
    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 57 (1985), S. 4146-4148 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Present works describe the developments the low cost R-Fe-B sintered permanent magnets. Three different didymiums are chosen for the low cost mixtures of rare-earth elements. The studied alloy compositions are Fe-(32.5–34.5)wt. %R-(1–1.6)wt. %B, where R elements are didymium (Nd-10wt. %Pr), 5Ce-didymium (Nd-15%Pr-5%Ce), and 40 Ce-didymium (Nd-10%Pr-40%Ce). The specimens were prepared by the conventional powder metallurgical techniques. The best magnetic properties obtained in this studies are Br=13.2 kG, iHc=10.2 kOe, and (BH)max=40 MGOe with the Fe-33.5% (5Ce-didymium)-1%B alloy. Temperature dependence of iHc of this alloy is almost comparable to that of the Nd-Fe-B alloys.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 4167-4169 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fe-Cr-Co ductile alloys produce magnetic properties comparable to those of Alnico permanent magnets family, up to (BH)max=91.2 kJ/m3(11.4 MGOe). It is technologically known that the addition of Ti to the Fe-Cr-Co alloys extends the α-phase region of system and improves the magnetic properties. The purpose of this work is to study the effect of Ti on microstructures and magnetic properties of Fe-Cr-Co alloys. The microstructures of Fe-25 wt.% Cr-12 wt.% Co alloys with or without Ti melted in air or in vacuum, were studied by optical microscopy, electron probe microanalysis (EPMA), and transmission electron microscopy (TEM). The alloys without Ti exhibit the precipitates of Cr23C6 carbide and Cr2N nitride a along the grain boundary or inside grain. These carbides and nitrides form the Cr-depleted zone around them. However, the addition of Ti suppressed the formation of Cr-depleted zone, in forming the Ti(C,N), and the magnetic properties are improved.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 4252-4254 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effective permeability ( μeff) of the ring Sendust alloys (Fe-9–10 wt. % Si-5–7 wt. %Al), molded with Epoxy resin, was measured in the temperature range of −10 to 70 °C. The μeff of the alloys in molded condition measured at 20 °C is smaller than that in unmolded condition. The high values of the μeff at 20 °C of the molded alloys were obtained from the alloys in which magnetostriction constants (λs) were close to zero. The temperature dependencies of the μeff for the studied alloys in the unmolded condition are very similar, but after molding they are classified into four variations depending on the value of λs. When the alloys have large positive or negative values of λs, the μeff increases or decreases monotonically with increasing temperatures, but for the alloy with λs (approximately-equal-to)0, the μeff temperature dependence is complex. These behaviors of the μeff with temperature are interpreted on the basis of the induced stress, initiating from the differences in thermal expansion between alloys and Epoxy resin. The μeff of the molded alloys was mainly dominated by the induced uniaxial magnetic anisotropy (Ku) by the tangential and axial compressive stresses in the molded ring alloys.
    Type of Medium: Electronic Resource
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