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  • 1
    Electronic Resource
    Electronic Resource
    Melt-spun PrCo5 and related magnet materials: Coercivity enhancement by carbon addition (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4651-4659 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated melt-spun Pr-Co alloys with the objective of optimizing their permanent magnet characteristics. Among a variety of elemental additives studied, carbon was found capable of significantly improving the properties, the coercivity in particular. For binary Pr-Co systems optimum values of the remanence, Br=5.7 kG, intrinsic coercivity, Hci=5.8 kOe, and energy product, (BH)max=4.7 MG Oe, were obtained from the Pr16Co84 composition. These values were enhanced to Br=5.8 kG, Hci=16.5 kOe, and (BH)max=7.4 MG Oe for Pr18Co76C6. In both cases the melt-spun ribbons were principally composed of PrCo5. The 16.5 kOe coercivity of the carbon-containing ribbons is the highest ever reported for a PrCo5-based material. Two new rare earth-cobalt phases were tentatively identified during the course of this work: PrCo7 (hexagonal TbCu7 structure) and PrCo2Cx (cubic MgCu2 structure). Survey results for other melt-spun, RCo5-based alloys are also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354355
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  • 2
    Electronic Resource
    Electronic Resource
    Formation of R2Fe14C compounds (R=Y, Ce) by rapid solidification (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7727-7730 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report formation of the Nd2Fe14B-type compounds Y2Fe14C and Ce2Fe14C via heat treatment of melt-spun ribbons. The existence of several R2Fe14C (R≡rare earth) phases has been documented in the literature, but the light R compounds are extremely difficult to prepare by conventional procedures. In particular, the yttrium compound was not found in a study of the equilibrium Y-Fe-C phase diagram, and previously available information on Ce2Fe14C was obtained only by extrapolation of data for Mn-substituted materials. We have prepared the Pr, Nd, Sm, Gd, Dy, Er, and Tm carbides as well, and we analyze the behavior of the Curie temperature through the series using a simple mean-field model. The analysis indicates that the R-Fe exchange interaction energy is significantly smaller for the heavy-R, as compared with the light-R, members of the series.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347548
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  • 3
    Electronic Resource
    Electronic Resource
    Direct determination of praseodymium valence in Pr2(CoxFe1−x)14B (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 676-679 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using x-ray-absorption near-edge spectroscopy (XANES) the Pr valence in the pseudoternary Pr2(CoxFe1−x)14B compounds has been directly determined. Praseodymium LIII edge XANES structures were obtained for the x=0, 0.3, 0.5, 0.7, and 1 compositions spanning the entire Co concentration range. It is found that the Pr valence is constant through the series and is identical to that in formally trivalent praseodymium acetate. The results demonstrate that the anomalous variation of the magnetocrystalline anisotropy with x in the Pr2(CoxFe1−x)14B compounds vis-à-vis their Nd-based counterparts does not arise from a Pr valence instability, as has been speculated in the literature, but must originate elsewhere. For comparison purposes XANES spectra for some relevant Ce and Nd materials are also reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351851
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  • 4
    Electronic Resource
    Electronic Resource
    Coercivity enhancement of melt-spun Nd-Fe-B ribbons using low-level Cu additions : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5823-5825 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have explored the impact of low-level Cu additions on the magnetic properties of melt-spun Nd-Fe-B ribbons. The addition of 0.5 at. % Cu enhances the intrinsic coercivity as much as 30% over that of Cu-free materials. Transmission electron microscopy analyses demonstrate that Cu segregates preferentially to the intergranular regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347861
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  • 5
    Electronic Resource
    Electronic Resource
    Neutron powder diffraction study of Tb2Fe14B : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5884-5886 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report Rietveld analyses of neutron powder diffraction data on Tb2Fe14B at 8 and 293 K. Our results confirm the inferences from magnetization measurements that (i) all eight magnetic moments are collinear with the c axis, (ii) the Tb and Fe moments are antiparallel, and (iii) the Tb moments approach their free ion value at low temperatures. Systematics of the variation of the lattice constants and nuclear position parameters across the R2Fe14B series are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353510
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetostriction and torque response of Tb0.5Dy0.5Fe2/Fe composites (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8653-8657 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Equivolume composites of melt-spun Tb0.5Dy0.5Fe2 in an Fe matrix have been consolidated by hot pressing over a range of temperatures. We find that both the magnetic field dependence of the magnetostriction λ(H) and the torque response Rτ of these materials in a sensor configuration depend strongly on the consolidation temperature. As the hot press temperature increases, λ(H) becomes sharper, generating higher strains at lower applied fields, higher values of the maximum slope dλ/dH, and more nearly saturated λ(H) at the maximum applied field of 19 kOe. These changes in magnetostriction are closely correlated with the observed response of the composites in a torque test. For a composite hot pressed at 755 °C we observe Rτ=6.3 G/100 ppm, a value which is twice that obtained for material consolidated at 550 °C and nearly a factor of three greater than the response of maraging steel. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373592
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  • 7
    Electronic Resource
    Electronic Resource
    Structural and magnetic properties of R3(Fe,T)29 compounds : 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. 6144-6146 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the formation of several members of the recently discovered class of R3(Fe,T)29 compounds and some of their intrinsic properties. Focusing on materials with T=Ti and Cr, we have prepared R3(Fe,Ti)29 (R=Ce, Pr, Nd, Sm) and R3(Fe,Cr)29 (R=Ce, Nd, Sm) compounds which all feature the novel monoclinic crystal structure first established for Nd3(Fe,Ti)29. In each of the Ti- and Cr-containing groups the Ce member has the smallest magnetization, Curie temperature, and unit cell, suggesting that the Ce ion is tetravalent, or nearly so, in this family of materials. We observed no evidence of R3(Fe,Ti)29 phase formation for R=Y, Gd, Dy, and Er. Our magnetization measurements indicate that only Nd3(Fe,Ti)29 and Nd3(Fe,Cr)29 exhibit spin reorientations, at temperatures of 235 and 145 K, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358334
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  • 8
    Electronic Resource
    Electronic Resource
    Resonant ultrasound measurements of elastic constants in melt-spun R2Fe14B compounds (R=Ce, Pr, Nd, Er) : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6625-6627 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements are reported of the longitudinal and transverse elastic moduli of the R2Fe14B compounds having rare-earth component R=Ce, Pr, Nd, and Er. A resonant ultrasound technique was used to determine the elastic constants on hot-pressed, melt-spun samples which are essentially isotropic, polycrystalline specimens of the four compounds. The results for Nd2Fe14B, which agree well with previous studies, and Er2Fe14B exhibit clear signatures of the spin reorientations which occur in those compounds. No such signature appears in the data for Pr2Fe14B, consistent with the fact that no spin reorientation occurs in that material. The ultrasonic attenuation of each sample has also been measured and it has been found that it shows features in the vicinity of spin reorientations (Nd2Fe14B, Er2Fe14B) and the Curie point (Ce2Fe14B).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356875
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  • 9
    Electronic Resource
    Electronic Resource
    Structural, magnetic, and magnetocaloric properties of (Hf0.83Ta0.17)Fe2+x materials : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5998-6000 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the sensitivity of structural, magnetic, and magnetocaloric properties of (Hf0.83Ta0.17)Fe2+x alloys (x=−0.18, −0.09, −0.02, 0.00, 0.09, 0.26) to Fe content. As-cast samples for all x consist essentially exclusively of hexagonal MgZn2-type material. Via magnetization and differential scanning calorimetry measurements we find that all the alloys except x=0.26 feature both a ferromagnetic→antiferromagnetic (FM→AFM) transition at temperature T0 and a Néel transition. The most abrupt FM→AFM transition occurs in the x=−0.02 material which also exhibits the lowest T0 and largest low-temperature moment. We report a magnetocaloric property, the field-induced entropy change ΔS, for the x=0.00 and x=±0.09 alloys. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362133
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  • 10
    Electronic Resource
    Electronic Resource
    Phase formation in melt-spun Nd-Fe-Mo-Ti alloys : 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. 6056-6058 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report for the first time the range of ThMn12-type crystal structure formation in melt-spun Nd-Fe-Mo-Ti ribbons. These materials, which combine the melt-spun microstructure with the favorable intrinsic magnetic properties of the NdFe12−x(Mo,Ti)x phase, are important as precursors to the formation of hard magnetic materials by nitrogen absorption. Alloys with compositions Nd1.15Fe10+xMo2−2xTix (0≤x≤1), which grade the composition smoothly between the two end point alloys Nd1.15Fe10Mo2 and Nd1.15Fe11Ti, were melt spun at quench wheel velocities 5 m/s≤vs≤30 m/s. From x-ray diffraction patterns we construct a phase formation diagram as a function of Ti content x and wheel speed vs. We find that the desired ThMn12 structure is obtained only in ribbons quenched at low vs. At higher speeds, the ribbons quench instead into the disordered TbCu7-type crystal structure. Further, the ThMn12 structure is considerably less stable at the Ti-rich end of the composition range than at the Mo-rich end: for Nd1.15Fe10Mo2, the ThMn12 structure is obtained for vs≤17.5 m/s, whereas in Nd1.15Fe11Ti only ribbons quenched at vs=5 m/s are of the ThMn12 type. Heat treatments of Nd1.15Fe11Ti ribbons melt spun at 30 m/s confirm the relatively difficult formation of the ThMn12 structure type; annealing temperatures in excess of 1000 °C are required to form the ThMn12 crystal structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358364
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