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  • 1
    Electronic Resource
    Electronic Resource
    Hard magnetic properties of melt-spun R(Fe,M)12 nitrides (R=Nd or Pr; M=Mo or V) (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 988-992 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The hard magnetic properties of nitrided melt-spun R(Fe,M)12 (R=Pr and Nd, M=V and Mo) ribbons have been investigated. Hard magnetic powders were prepared by vacuum annealing of ground ribbons in the temperature range from 700 to 950 °C and subsequent nitrogenation. For NdFe10.5Mo1.5Nx and PrFe10.5Mo1.5Nx powders, coercivities as high as 10.4 and 4.5 kOe at room temperature, respectively, were achieved by carefully controlling the nitrogenation process. The coercivity strongly depends on the preparation route, i.e., annealing temperature as well as nitrogenation temperature and time. By the detailed investigation of the influence of these conditions, the optimum process parameters were determined. The coercivity mechanism of melt-spun NdFe10.5Mo1.5Nx powders shows characteristics of a randomly oriented single domain particle system. Poor coercivities have been obtained for Nd(Fe,V)12 and Pr(Fe,V)12. In these cases as well as for not optimally nitrogenated Nd(Fe,Mo)12, the low coercivity of the nitrided powders is related to (i) too large grain sizes, (ii) the presence of α-Fe additional to the ThMn12-type phase, or (iii) a nonhomogeneous nitrogenation of the powder. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373766
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  • 2
    Electronic Resource
    Electronic Resource
    First order magnetization processes in Nd(Fe, M)12Cy compounds (M=V, Ti, Mo) (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5278-5280 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization measurements on Nd(Fe, M)12Cy (M=Ti, V, Mo) with ThMn12-type structure have revealed well developed first order magnetization processes (FOMPs) when an external field is applied perpendicular to the c axis. The FOMPs depend on carbon concentration, temperature, and the type of M element. The FOMPs appear at a certain carbon concentration and at temperatures below 150–100 K. The FOMP fields of NdFe12−xVxCy are independent of the V content in the range x=1.25–2.0, which is due to the small change of the anisotropy field within this range. No FOMP has been found in the nitrides of the same parent alloys. The evaluation of the crystal field (CF) parameters shows that the higher-order CF parameters of the Nd ions play a key role in producing the observed type-II FOMP. The temperature dependence of the FOMPs is due to the thermal evolution of the anisotropy constants Ki (i=1,2,3) of the carbides. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373320
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  • 3
    Electronic Resource
    Electronic Resource
    Microstructure and domain structures of Sm0.56GdxDy0.44−x(Co0.68Fe0.22Cu0.08Zr0.02)7.22 magnets with low temperature coefficients (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1053-1056 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructure and domain structures of high performance temperature-compensated sintered magnets with composition of Sm0.56GdxDy0.44−x(TM)7.22 (TM=Co0.68Fe0.22Cu0.08Zr0.02)7.22 (0.0≤x≤0.4) have been investigated by using electron microscopy and magnetic force microscopy. Both microstructure and magnetic properties of these magnets show a significant dependence on the content of heavy rare earth Gd and Dy. The intrinsic coercive force increases significantly with increasing Gd content. It is found that there are two different types of grains in the magnets, which show different domain structures. The larger magnetocrystalline anisotropy, larger cell size, and coarser grain boundary region give rise to a higher coercivity in the Gd-rich magnets. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370846
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic properties of RFe10.5Mo1.5Cx and their nitrides : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6640-6642 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: RFe10.5Mo1.5Cx (R=Y, Nd, and Dy; x=0–0.6) have been successfully synthesized by arc melting, then followed by a gas-solid phase reaction to form YFe10.5Mo1.5CxNy. X-ray diffraction studies and thermomagnetic analysis show that all samples are of good single phase, and carbides and carbon nitrides remain the ThMn12-type structure. The addition of carbon atoms has an effect of improving the magnetic properties. Both Curie temperature and saturation magnetization are found to be increased with carbon concentration x in the RFe10.5Mo1.5Cx series, and the carbon atoms also affect the magnetocrystalline anisotropy. The easy axial anisotropy of NdFe10.5Mo1.5Cx and DyFe10.5Mo1.5Cx is enhanced. As to the nitrides, the results indicate that YFe10.5Mo1.5CxNy possess a higher Curie temperature and a larger saturation magnetization than YFe10.5Mo1.5Ny, which is of significance in the technical applications. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367581
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of interstitial nitrogen on the structural and magnetic properties of NdFe10.5V1.5Nx (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 2700-2704 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The NdFe10.5V1.5Nx nitrides crystallize in the ThMn12-type structure. The nitrogen atoms occupy interstitial sites, and their most important effects are on the crystal fields around the rare earth ion sites. The variation of anisotropy fields of NdFe10.5V1.5Nx as a function of the nitrogen content x is presented. The crystal field interaction parameters are determined by using single-ion model. In the light of this study, high performance magnetic powders based on NdFe10.5V1.5Nx were successfully prepared. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366991
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  • 6
    Electronic Resource
    Electronic Resource
    Nitrogenation of the magnetic compound R(Fe,M)12 (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 1983-1987 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusion mechanism of nitrogen atoms in ThMn12-type crystal structure compounds was investigated by using x-ray diffraction, Mössbauer spectroscopy measurements, thermopiezic analysis, and differential thermal analysis. The studies indicate that the distribution of nitrogen atoms in a R(Fe,M)12 particles with intermediate N content is characterized by a nitrided region and an unnitrided region. The results confirmed that this two-phase region is stable, and the nitrogen atoms do not diffuse further into the particle. Based on the characteristics of the nitrogenation, a trapping diffusion model is applied to the R(Fe,M)12 system. On the basis of this study high performance magnetic powders of NdFe10.5Mo1.5Nx were successfully prepared. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366926
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  • 7
    Electronic Resource
    Electronic Resource
    57Fe Mössbauer study of the interstitial nitrogen atom effects of NdFe10.5V1.5Nx : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6923-6925 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic and 57Fe Mössbauer spectra measurements were carried out to study the interstitial nitrogen atom effects in the NdFe10.5V1.5Nx (0≤x≤2.1) compounds. It is found that saturation magnetization, magnetocrystalline anisotropy, hyperfine fields, and isomer shifts of NdFe10.5V1.5Nx are strongly enhanced upon nitrogenation, due to magneto-volume effects and chemical bonding effects of nitrogen atoms. On the basis of the variation of isomer shifts and hyperfine fields as a function of nitrogen concentration, and by using a set of phenomenological formulas, the contributions of magneto-volume effect and the chemical bonding effect to the hyperfine parameters are successfully separated. The pure magneto-volume effect and the chemical bonding effect of the nitrogen atoms will give a positive contribution to the average hyperfine fields and isomer shifts of the Fe atoms in the NdFe10.5V1.5Nx nitrides. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367553
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic properties and magnetic domain structures of NdFe10.5Mo1.5 and NdFe10.5Mo1.5Nx (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3290-3292 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We succeed in preparing anisotropic magnetic powders with high performance based on the NdFe10.5Mo1.5Nx nitrides. The properties of these materials are favorable for permanent magnet application. The domain structures of the NdFe10.5Mo1.5 and NdFe10.5Mo1.5Nx were studied by using magnetic force microscopy. Upon nitrogenation, a domain structure transition from complex maze to simple stripe was found. This transition is due to the strongly uniaxial magnetocrystalline anisotropy induced by interstitial nitrogen atoms. Together with magnetic measurements, we have calculated the domain wall energy γ, exchange constant A, domain wall thickness δ, and critical single-domain particle size Dc of NdFe10.5Mo1.5 and NdFe10.5Mo1.5Nx. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120315
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of hard magnetic materials: PrFe10.5V1.5Nx (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 3044-3046 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The PrFe10.5V1.5 intermetallics and their nitrides were successfully synthesized. In terms of magnetocrystalline anisotropy, PrFe10.5V1.5Nx are characteristics of an easy axis from 0 K to Curie temperature, with an anisotropy field up to 152.9 kOe at 1.5 K and 108.4 kOe at room temperature. In combination with a high Curie temperature of 820 K and a large saturation magnetization of 157.46 emu/g at 1.5 K and 142.77 emu/g at room temperature, these nitrides are favorable for permanent magnet applications. As a preliminary attempt, magnetic powders based on PrFe10.5V1.5Nx were obtained with a maximum energy product of 16.0 and 28.8 MGOe at room temperature and 1.5 K, respectively. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118744
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  • 10
    Electronic Resource
    Electronic Resource
    Mössbauer study of the (Fe1−xNix)4N compounds (0≤x≤0.6) (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2343-2345 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single phase γ'-Fe4N type (Fe1−xNix)4N compounds (0≤x≤0.6) have been synthesized by heating iron-nickel oxalates under a mixture stream of NH3 and H2. The compounds were investigated by x-ray diffraction and Mössbauer spectroscopy. The results confirm that the lattice constants decrease with increasing content of nickel. Compared with the same compositional Fe1−xNix alloys, the average expansion of the unit cell (δV/V) is 16.7% for γ-Fe-Ni alloys. The Mössbauer study shows that the substitution of nickel atoms for iron atoms has a tendency to locate at the corner sites. When x=0.5, all of the corner sites are completely occupied by nickel atoms. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113977
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