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  • 1
    Electronic Resource
    Electronic Resource
    Composition and temperature dependence of coercivity of Nd-Fe-B alloys crystallized from the amorphous state (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5552-5552 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: As a first step to study the role of second phases in achieving excellent hard magnetic properties in Nd-Fe-B permanent magnets we have prepared Nd-Fe-B alloys, near the Nd2Fe14B composition, with a maximum variation of 10 at. % Nd and 5 at. % B. The alloys were first quenched into an amorphous state by melt spinning, as previous studies on crystallization kinetics suggest better control on the microstructure and hence better hard magnetic properties of the recrystallized alloys. For all compositions with Nd concentrations 1 at. % greater than that of Nd2Fe14B the intrinsic coercivity Hci is above 1.2 T at 100 °C. For a constant Nd/B ration, Hci increases monotonously with Nd constant while for compositions where even small amounts of α. Fe form as a crystallization product Hci shows a sharp drop. On the other hand, it appears that B content is much less significant in determining Hci. The temperature dependence of Hci is almost linear for all compositions between 20 and 200 °C and is much better than that for sintered materials. Hci at room temperature of our samples is about 20% higher than that of commercial rapidly quenched materials with similar composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342334
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  • 2
    Electronic Resource
    Electronic Resource
    A new metastable phase in the Nd-Fe-B system (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5723-5725 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new metastable compound has been obtained during the crystallization of Fe-rich Nd-Fe-B amorphous alloys. The composition range for the precipitation of this phase is Nd4.5±1Fe82.5±5B12.5±3.5. A single phase, however, is obtained in a much restricted composition range. The amorphous alloy has a Curie temperature of 466 K and crystallizes at 852 K (for a heating rate of 40 K min−1 ) into the new metastable compound which has a body-centered-cubic structure with a=1.238 nm. Its Curie temperature is 548 K. Upon heating above 975 K, this phase transforms into Nd2Fe14B, NdFe12B6, and α-Fe. It appears that it is necessary to start from a truly amorphous state in order to form the new phase, otherwise, a competing body-centered-cubic phase Nd2Fe23B3 forms. X-ray diffraction and Mössbauer spectroscopy data are also presented and compared to that of Nd2Fe23B3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342238
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of oxygen impurities on the crystallization mechanism of NiZr2 metallic glasses (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2441-2446 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of oxygen impurities on the crystallization mechanism of NiZr2 metallic glasses was studied. For this glass system, the first crystallization product is the metastable E93(cF96) cubic structure instead of the equilibrium C16(tI12) tetragonal structure. A possible mechanism for the formation of this metastable phase has previously been put forth. The hypothesis is that oxygen forms a semipermanent bond with Zr resulting in the oxygen atom being surrounded by six Zr atoms in octahedral configuration which act as nucleation sites for the E93 cubic phase. Hydrogenation of the amorphous composition eliminates the nucleation sites required for the formation of this metastable cubic phase, thereby allowing the glass to crystallize directly into the stable tetragonal C16 phase, and thus providing strong evidence in support of the proposed crystallization mechanism. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1334920
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  • 4
    Electronic Resource
    Electronic Resource
    Mechanical properties of Al–Y–Ni amorphous ribbons (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3967-3970 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mechanical properties for two series of amorphous Al–Y–Ni ternary alloys were measured. Both series of alloys can be divided into two distinct groups. Those whose primary crystallization proceeds by growth of quenched-in Al nuclei and those which show a clear glass transition and their crystallization product is more complex. The Young's modulus, ranging from 82.3 to 45.5 GPa in these series of alloys, is found to be correlated to the crystallization temperature and thermal behavior as well as the crystallization product implying that the mechanical properties depend on the short-range order in the glass. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361824
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  • 5
    Electronic Resource
    Electronic Resource
    Spin polarized neutron scattering study of NiCo/Cu multilayers : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4769-4771 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spin polarized neutron reflectometry measurements were performed on Ni80Co20/Cu multilayers with a Cu spacer thickness of 20 A(ring), corresponding to the second oscillation peak in the magnetoresistance of the NiCo/Cu multilayer system. Measurements in a 15 Oe field indicate a nearly perfect antiferromagnetic stacking of the magnetic moments in successive Ni80Co20 layers. The existence of a small magnetic anisotropy in these magnetically soft multilayers leads to the canting of the magnetic moments at an angle of ∼70° with respect to the neutron spin polarization. This interlayer antiferromagnetic coupling can be suppressed by an applied field of ∼200 Oe. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361667
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  • 6
    Electronic Resource
    Electronic Resource
    Formation of Nd(Fe1−yCoy)2 in rapidly quenched Nd13.75(Fe1−xCox)80.25B6 (x=0−0.5) alloys : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4833-4835 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray diffraction patterns of overquenched Nd13.75(Fe1−xCox)80.25B6 (x=0−0.5) ribbons show fine grains of the 2–14–1 phase in an amorphous matrix. The ribbons, subsequently annealed at 975 K for 5 min, were investigated using quantitative x-ray structural analysis. The results indicate that in addition to the main 2–14–1 phase, all the samples have approximately 1 vol % of the γ-Nd phase. The existence of the Nd(Fe1−yCoy)2 phase is established for x≥0.25 and its amount reaches up to 5.4 vol % for higher Co concentrations. From an interpolation of the measured lattice parameters of the 1–2 phase, the Co content is estimated to vary from y=0.38 to y=0.58 for this series of alloys. Using differential scanning calorimetry (DSC) the enthalpy of formation of the 1–2 phase in overquenched Nd13.75(Fe0.7Co0.3)80.25B6 ribbons is found to be about 3 kJ/mol. The activation energy necessary for the formation of the 1–2 phase, for the same composition, as determined from the Kissinger relation is 2.2±0.1 eV. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361623
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  • 7
    Electronic Resource
    Electronic Resource
    Structure and magnetic properties of mechanically alloyed Nd(Fe,V)12Nx compounds : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5519-5521 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure and magnetic properties of Nd(Fe,M)12Nx (M=Ti,Mo,V) compounds prepared by mechanical alloying (MA) have been studied using x-ray diffraction and magnetic measurements. It is found that after annealing, single-phase Nd(Fe,V)12 compounds can be obtained over a large composition range, but can only be obtained in Nd(Fe,V)11 after MA. The crystallization of stoichiometric compounds at 750–950 °C always produces a small amount of α-Fe(V) in addition to the 1:12 phase. Below 750 °C, the crystallization is not complete and large amounts of α-Fe(V) are present. When nitriding at 450 °C, the α-Fe(V) phase disappears accompanied by the formation of an amorphous phase and a 1:7 nitride phase. The crystallized phase retains the 1:12 structure when nitriding at 480 °C. The highest coercivity of 8.8 kOe has been obtained for the NdFe10.5V1.5Nx compound. The difference between the coercivities of MA Nd(Fe,V)12Nx, Nd(Fe,Mo)12Nx, NdFe11TiNx, and Sm2Fe17Nx compounds is attributed to their different crystallization behavior and phase stability during nitrogenation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362296
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  • 8
    Electronic Resource
    Electronic Resource
    Thermal stability of nanostructured Sm2Fe17Cx compounds prepared by ball milling : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5536-5538 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal stability of ball-milled nanocrystalline Sm2Fe17Cx interstitial compounds has been investigated. Sm2Fe17Cx decomposes into a mixture of phases upon annealing above a certain decomposition temperature, Td1, which depends on the carbon concentration in the compound. Annealing above a certain temperature Td2((approximately-greater-than)Td1), the Sm2Fe14C phase starts to form. The amount of the Sm2Fe14C phase increases with increasing annealing temperature at the expense of the Sm2Fe17 carbide until Tr1, at which temperature Sm2Fe14C starts to recombine with other phases to form the Sm2Fe17 carbide. For the starting composition with x〈1.5, the Sm2Fe17Cx single phase can be recovered above the recovery temperature Tr2((approximately-greater-than)Tr1). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362301
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  • 9
    Electronic Resource
    Electronic Resource
    Temperature dependence of coercivity in MnBi : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6275-6277 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In contrast to most ferromagnetic materials, the low-temperature phase of MnBi exhibits an increased coercivity, Hc, with temperature. μ0Hc has a value of 0.2 T at room temperature, and rises dramatically to a maximum value of 1.9 T at 550 K. In the temperature region near its maximum value, Hc is much larger than that of Nd-Fe-B and has a very-low-temperature coefficient. For this reason, MnBi has a great potential as a permanent magnet material at high temperatures. To describe the temperature dependence of Hc, we develop a hybrid domain-wall pinning model which combines Hilzinger and Kronmüller's scaling theory for an anisotropic domain wall with Gaunt's theory of thermal activation. The hybrid model gives an excellent fit to the temperature dependence of Hc and provides good estimates for the domain-wall energy and thickness over the temperature range studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352668
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  • 10
    Electronic Resource
    Electronic Resource
    Metastable RFe7 compounds (R=rare earths) and their nitrides with TbCu7 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. 4605-4607 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: RFe7 compounds with the TbCu7 structure have been synthesized by annealing of mechanically alloyed powders. The lattice constants a and c decrease with increasing atomic number of the rare earths except for Ce which has a different valence state. Introduction of nitrogen interstitial atoms into the structure results in a ∼6.0% volume expansion. In addition, nitriding gives rise to a dramatic enhancement of the magnetic properties of the compounds. Curie temperatures are increased by ∼300 °C upon nitriding. RFe7 nitrides with R=Sm, Tb, Dy, and Ho have high coercivities. A substantial enhancement in the magnetic remanence for the RFe7 nitrides with R=Tb, Dy, and Ho is attributed to the magnetic exchange coupling between grains of nanocrystalline structure in the powders. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361739
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