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  • 1
    Electronic Resource
    Electronic Resource
    Neutron-diffraction and Mössbauer effect study of the preferential silicon site occupation and magnetic structure of Nd2Fe14−xSixB (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6798-6809 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A neutron-diffraction study of Nd2Fe14−xSixB has shown that silicon preferentially occupies the 4c site in the transition-metal sublattice in Nd2Fe14B. Silicon also exhibits a moderate preference for the 8j1 site, is almost excluded from the 16k2 site, and avoids the 16k1, 8j2, and 4e sites. The silicon site occupancy is correlated with a preference for a silicon atom to have rare-earth atoms in its coordination environment. The Mössbauer spectra of Nd2Fe14−xSixB have been fit with a model which takes into account the distribution of near-neighbor environments of an iron atom due to the presence of silicon. These fits show that the substitution of silicon in the near-neighbor environment of an iron atom primarily influences the long-range contributions to the hyperfine field experienced by the iron. The mechanism for the increase in the Curie temperature when silicon is added to Nd2Fe14B-type magnets is more subtle than previously believed, but can be explained by the relative decrease in the proportion of short iron-iron bonds when silicon is substituted for iron.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355080
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  • 2
    Electronic Resource
    Electronic Resource
    Neutron diffraction and Mössbauer effect study of several Nd2Fe17−xAlx solid solutions : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6029-6031 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Aluminum-substituted Nd2Fe17−xAlx solid solutions with x=2.30, 4.44, 6.13, 8.00, and 9.40 have been studied by neutron diffraction and Mössbauer spectroscopy. A Rietveld analysis of the neutron scattering indicates that the aluminum atoms have a high initial affinity for the 18h site, show a high affinity for the 6c site at high aluminum concentrations, and are absent from the 9d site at all aluminum concentrations. The Mössbauer spectra show a maximum in both the maximum and weighted average hyperfine field for x≈2. This indicates that the lattice expansion which occurs with aluminum substitution is sufficient, at least for small values of x, where magnetic dilution is small, to enhance the intrasublattice coupling between the iron moments, and to increase the magnetic hyperfine fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353459
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  • 3
    Electronic Resource
    Electronic Resource
    A Mössbauer-effect study of a series of R2Fe14C hard magnetic materials : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6040-6042 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The 57Fe Mössbauer-effect spectra of the series of hard magnetic materials, R2Fe14C, where R is Nd, Gd, Tb, Dy, Ho, and Lu, have been measured at 295 K. All of these carbides exhibit uniaxial magnetic anisotropy. The spectra resemble those obtained for the related R2Fe14B compounds and have been fit with the model used earlier for Nd2Fe14B. The magnitude of the hyperfine field on each site, as a function of rare earth, parallels the Curie temperature; the maximum hyperfine fields and the maximum Curie temperature are observed for Gd2Fe14C. A linear correlation is observed between the hyperfine fields on the six sites in the analogous borides and carbides; however, these fields are systematically smaller in the carbides. The decrease in the tetragonal unit cell c-axis length in the carbides apparently reduces the exchange interactions between the 8j and 16k iron layers and hence reduces the moments. The isomer shift on each site decreases as the atomic number of the rare earth increases, whereas the quadrupole interactions are independent of rare earth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347763
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  • 4
    Electronic Resource
    Electronic Resource
    Neutron-diffraction and Mössbauer-effect studies of Pr2(Fe1−xMnx)14B (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4762-4764 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A neutron-diffraction investigation of a series of Pr2(Fe1−xMnx)14B samples, with x values of 0.00, 0.11, 0.22, 0.30, and 0.35, reveals a preference for the manganese to occupy the 8j2 transition-metal site,the transition-metal site with the largest Wigner–Seitz cell volume. Similar site occupancies have been reported previously for Er2(Fe1−xMnx)14B and Y2(Fe1−xMnx)14B. An analysis of the 295-K Mössbauer spectrum of Pr2(Fe0.89Mn0.11)14B indicates that the internal hyperfine fields on the six iron sites are more substantially reduced from those found in Pr2Fe14B than would be expected from a simple magnetic dilution with manganese. The extent of the field reduction for a specific site increases with the number of manganese near neighbors for the site. Fits of the Mössbauer spectra of Pr2(Fe0.78Mn0.22)14B, Pr2(Fe0.70Mn0.30)14B, and Pr2(Fe0.65Mn0.35)14B, which are paramagnetic at room temperature, give quadrupole splittings consistent with the quadrupole interactions in Pr2Fe14B.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344778
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  • 5
    Electronic Resource
    Electronic Resource
    A neutron diffraction and Mössbauer effect study of the magnetic structure of Y2(Fe1−xMnx)14B : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6149-6151 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic structures of a series of Y2(Fe1−xMnx)14B samples, with x equal to 0.03, 0.10, 0.25, and 0.37, have been studied by powder neutron diffraction and Mössbauer spectroscopy. Y2(Fe0.97Mn0.03)14B and Y2(Fe0.9Mn0.1)14B are ferromagnetic at both 295 and 85 K, Y2(Fe0.63Mn0.37)14B is paramagnetic at both 295 and 85 K, whereas Y2(Fe0.75Mn0.25)14B is paramagnetic at 295 K and is partially ordered at 78 K. The magnetic structure of Y2(Fe0.75Mn0.25)14B is explained in terms of the preferential Mn occupancy of the transition metal 8j2 site in the Y2Fe14B structure. Small amounts of Mn located in this site are very effective in disrupting the long-range ferromagnetic coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350025
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  • 6
    Electronic Resource
    Electronic Resource
    A neutron diffraction and Mössbauer effect study of the magnetic properties of Pr2Fe17 and Pr2Fe17N2.6 (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 504-512 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The neutron diffraction powder patterns of Pr2Fe17 and Pr2Fe17N2.6 have been measured at 295 K and refined within the Th2Zn17 structure type to give the structural changes which occur upon nitrogenation; changes which include a 6.4% expansion of the unit cell volume. The Mössbauer spectra of Pr2Fe17 and Pr2Fe17N2.6 have been measured between 85 and 295 K and analyzed with a model which is based on the Wigner–Seitz cell environment of each iron site, the basal orientation of the magnetization, and a comparison with the Mössbauer spectra of Nd2Fe17 and Nd2Fe17N2.6. Upon nitrogenation of Pr2Fe17, the 85 K-weighted average isomer shift increases from 0.049 to 0.156 mm/s, and the isomer shifts of the four crystallographically distinct iron sites increase in agreement with the increase found in their Wigner–Seitz cell volumes and the presence of a nitrogen near-neighbor for the 18f and 18h sites. The temperature dependence of the isomer shifts indicates an increase in covalency upon the formation of the nitride. Upon nitrogenation of Pr2Fe17, the 85 K-weighted average hyperfine field increases from 286.2 to 331.9 kOe, however, as is the case for the nitrogenation of Nd2Fe17, the increases on the 6c and 18f sites are much smaller than those observed on the 9d and 18h sites. These changes provide support for the band structure calculations of changes in the magnetic moments upon nitrogenation of Y2Fe17, Nd2Fe17, and Gd2Fe17.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355261
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  • 7
    Electronic Resource
    Electronic Resource
    A neutron diffraction and Mössbauer effect study of the magnetic properties of Pr2Fe17 and Pr2Fe17N2.6 (invited) (abstract) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6050-6050 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The neutron diffraction powder patterns of Pr2Fe17 and Pr2Fe17N2.6 have been measured at 295 K and refined within the Th2Zn17 structure type to give the structural changes which occur upon nitrogenation; changes which include a 6.4% expansion of the unit cell volume. The Mössbauer spectra of Pr2Fe17 and Pr2Fe17N2.6 have been measured between 85 and 295 K and analyzed with a model which is based on the Wigner–Seitz cell environment of each iron site, the basal orientation of the magnetization, and a comparison with the Mössbauer spectra of Nd2Fe17 and Nd2Fe17N2.6. Upon nitrogenation of Pr2Fe17, the 85-K-weighted average isomer shift increases from 0.049 to 0.156 mm/s, and the isomer shifts of the four crystallographically distinct iron sites increase in agreement with the increase found in their Wigner–Seitz cell volumes and the presence of a nitrogen near-neighbor for the 18f and 18h sites. The temperature dependence of the isomer shifts indicates an increase in covalency upon the formation of the nitride. Upon nitrogenation of Pr2Fe17, the 85-K-weighted average hyperfine field increases from 286.2 to 331.9 kOe, however, as is the case for the nitrogenation of Nd2Fe17, the increases on the 6c and 18f sites are much smaller than those observed on the 9d and 18h sites. These changes provide support for the band structure calculations of changes in the magnetic moments upon nitrogenation of Y2Fe17, Nd2Fe17, and Gd2Fe17.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354051
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  • 8
    Electronic Resource
    Electronic Resource
    A Mössbauer effect study of the microscopic magnetic properties of Nd2Fe17 and Nd2Fe17N2.6 (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4845-4854 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Mössbauer spectra of Nd2Fe17 and Nd2Fe17N2.6 have been measured at various temperatures between 78 and 295 K and analyzed with a model that is based on the Wigner–Seitz cell environment of each iron site, the orientation of the magnetization, and the magnetic moments as determined from either neutron-diffraction measurements or band-structure calculations. Upon nitrogenation of Nd2Fe17, the weighted average isomer shift increases from 0.060 to 0.164 mm/s and further the isomer shifts of the four crystallographically distinct sites increase in agreement with the increase observed in their Wigner–Seitz cell volumes and the presence of a nitrogen near neighbor for two of the sites. Upon nitrogenation of Nd2Fe17, the weighted average hyperfine field increases from 292.3 to 333.8 kOe. However, the increases on the 6c and 18f sites are much smaller than those observed on the 9d and 18h sites; changes which are in agreement with calculated changes in the magnetic moments upon nitrogenation of Nd2Fe17, Gd2Fe17, and Y2Fe17. The temperature dependence of the isomer shifts indicates an increase in covalency upon the formation of the nitride.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352049
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  • 9
    Electronic Resource
    Electronic Resource
    Electronic structures and magnetism of LaNi5–xFex compounds (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7311-7313 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic study of the magnetic moments and hyperfine interactions of the LaNi5–xFex compounds was performed using the spin-polarized tight-binding-linear-muffin-tin-orbital methods (TBLMTO). The calculated results were compared with neutron diffraction and Mössbauer experimental data and found to be in good agreement. Fe atoms exhibit more localized magnetic moments in LaNi5–xFex when the Fe content x is lower than 1.0. The calculated magnetic moments of the Fe atoms approach values as large as 2.5μB due to the dilution effect. The strong s–d hybridization between the Ni and La atoms and the neighboring Fe in the Fe-substituted samples results in a large transferred valence contribution to the total hyperfine field. It is found that the Fe and Ni magnetic moments decrease abruptly at a unit cell volume which is 5% smaller than the observed volume in LaNi4Fe due to the instability of the Fe magnetic moment. LaNi5 becomes ferromagnetic when the unit cell volume is larger than its original volume. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1357854
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  • 10
    Electronic Resource
    Electronic Resource
    Crystal and magnetic structures of LaNi5−xMnx (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6731-6733 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystallographic and magnetic properties of LaNi5−xMnx with x=1, 1.5, and 2, have been investigated using x-ray and neutron diffraction, vibrating sample magnetometer and superconducting quantum interference device measurements. All the samples crystallize in the hexagonal CaCu5-type (P6/mmm) structure. Manganese atoms preferentially occupy the 3g site in the LaNi5 structure. The bulk magnetization of the LaNi5−xMnx powder samples decreases rapidly as nickel is replaced by manganese. A ferrimagnetic model is applied to describe the magnetic structure of the LaNi5−xMnx samples for x=1.5 and 2. A ferromagnetic model gives the best fit of the neutron diffraction data for the LaNi4Mn sample. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372823
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