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  • Electronic Resource  (8)
  • 1985-1989  (8)
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  • Electronic Resource  (8)
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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic properties of R-Fe-B and R-Fe-Co-Al-B magnets (R=Pr and Nd) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5510-5512 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Permanent magnets based on the compositions Pr15Fe79B6, Nd15Fe79B6, Pr15Fe62.5Co16Al1B5.5, and Nd15Fe62.5Co16Al1B5.5 have been fabricated employing conventional powder metallurgical processes. Proper heat treatment has been found to improve magnetic properties. For example, in magnets of composition Pr-Fe-Co-Al-B, the heat treatment optimized in this study improved Br and (BH)max by about 5% and 10%, respectively, in comparison with conventional heat treatment reported in the literature. The temperature coefficients of magnetic properties have also been improved through Co and Al substitutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342319
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of Ga substitution on the magnetic properties of Nd2Fe14B, Pr2Fe14B, and PrCo5 (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3710-3712 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: R2Fe14−xGaxB (R=Pr and Nd) and PrCo5−xGax alloys were synthesized and examined by powder x-ray diffraction at room temperature and by magnetometry in the temperature range 4.2–1100 K. Lattice parameters, Curie temperature, spin-reorientation temperatures, anisotropy fields, and saturation magnetizations were determined. Phase analysis revealed that single-phase materials exist only for x≤1 in the case of 2:14:1 alloys and for x≤2 for 1:5 alloys. An increase in lattice parameters is observed upon Ga substitution in all cases. About 20 K increase in the Curie temperature is observed for 2:14:1 alloys, whereas there is a dramatic decrease in 1:5 alloys. Saturation magnetization values decrease upon Ga substitution. The anisotropy field is slightly enhanced by Ga addition in the Nd2Fe14−xGaxB system. Spin-reorientation phenomena in Nd2Fe14−xGaxB and PrCo5−xGax are strongly affected by Ga addition. The observed behavior is discussed in terms of preferential substitution of Ga atoms into the Nd2Fe14B-type crystal structure and random substitution into the CaCu5-type crystal structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340643
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A novel low-temperature preparation of several ferrimagnetic spinels and their magnetic and Mössbauer characterization (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5641-5643 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrafine subdomain particles of NiFe2O4, Ni0.5Zn0.5Fe2O4, and CoFe2O4 were prepared under mild hydrothermal conditions by precipitating from metal nitrates. Magnetic and Mössbauer effect measurements revealed the superparamagnetic nature of these ferrite particles. The crystallite sizes were in the range 5.0–20.0 nm with a very narrow particle size distribution. The magnetic properties and Mössbauer hyperfine parameters of these subdomain ferrite particles are somewhat different from those reported for multidomain bulk materials. The hydrothermal ferrite powders were found to sinter to almost theoretical density with little or no intergranular porosity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342283
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  • 4
    Electronic Resource
    Electronic Resource
    Structural and magnetic properties of Tm2−xDyxFe14B and Tm2Fe14−xCoxB alloys systems (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5540-5542 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Structural and intrinsic magnetic characteristics of Tm2−x Dyx Fe14 B (for the entire range of composition) and Tm2 Fe14−x Cox B (for x up to 4) were investigated in detail between 4.2 K and their Curie temperatures. Progressive replacement of Tm by Dy enhances the anisotropy field HA markedly. This was evidenced from the expansion of the uniaxial anisotropy temperature range determined by constructing the magnetic-phase diagram. These results are found to be in very good agreement with the crystal field theory, employing the second-order terms. Addition of Co in the lattice improves the magnetic ordering temperature, but reduces the saturation magnetization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342329
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  • 5
    Electronic Resource
    Electronic Resource
    Spin reorientation in substituted Nd2Co17 compounds (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3969-3971 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nd2Co17 alloy exhibits a saturation magnetization about 30% higher than that of Sm2Co17 at room temperature. However, the former is not a useful material for permanent magnet fabrication due to its basal plane anisotropy near room temperature. In this study, an attempt is made to investigate the effect of partial substitution of Nd2Co17 with other elements. In particular, alloys of the compositions Nd2−xSmxCo13Fe4 and Nd2Co13Fe4−xTx (where T=Zr or Mn) have been examined. The results obtained in this investigation show several interesting trends in the behavior of these alloys. Substitution of ∼20% Sm in Nd2−xSmxCo13Fe4 decreases the spin-reorientation temperatures from 613 to 224 K. Further, an increase in x up to 1.0 causes only a moderate decrease in the saturation magnetization but results in a considerable enhancement of the anisotropy field. Typical thermomagnetic curves of Nd2Co13Fe4−xTx (T=Zr,Mn) exhibit spin-reorientation temperatures. These results are discussed in terms of preferential substitution of Zr or Mn in this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340566
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  • 6
    Electronic Resource
    Electronic Resource
    Studies on high-density nickel zinc ferrite and its magnetic properties using novel hydrazine precursors (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3789-3791 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nickel zinc ferrites have been very widely used in the high-frequency applications. In our present study we have prepared Ni1−x Znx Fe2O4 (0≤x≤1) using novel hydrazinium metal hydrazinecarboxylate precursors. High densities (∼99%) have been obtained for all the ferrites sintered at relatively low temperatures, 1100 °C, in comparison with the conventional method (≥1200 °C). The variation of magnetic properties like magnetic moment, Curie temperature, and permeability with zinc concentration have been studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340615
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  • 7
    Electronic Resource
    Electronic Resource
    Prediction of magnetic phase diagrams of selected (RxR'1−x)2Fe14B systems (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3964-3966 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Preliminary experiments on (TmxDy1−x)2Fe14B have suggested the presence of axial, conical and planar regions in the magnetic phase diagram. Here we report the magnetic phase diagram for this and other mixed rare-earth systems, as predicted by second-order crystal field theory. The specific systems considered were those containing (Er or Tm) and (Pr, Tb, or Dy). It is shown that in these systems, which contain two rare-earth ions of opposite second-order Stevens coefficients, the occurrence of all three regions can be accounted for by second-order crystal field theory. The shapes of the phase boundaries are discussed in terms of the stabilization energies of the various rare earth ions. In particular, it was found that the relatively strong temperature dependence of the stabilization energies of Pr and Tm is responsible for low-temperature contractions of the planar and axial phases, respectively. This temperature dependence is attributed to the weaker exchange interaction [(g−1)J〈1] experienced by these ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340564
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  • 8
    Electronic Resource
    Electronic Resource
    Structure and magnetic properties of quaternary Pr2−xRxCo14B (R=Dy and Er) systems and their hydrides (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3972-3974 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single-phase materials of quaternary Pr2−xRxCo14B (R=Dy or Er), which crystallize in the Nd2Fe14B-type tetragonal structure, form for the compositions only up to about x=1.5. Measurements of lattice parameters and the bulk magnetization were carried out on these compounds and their hydrides. Saturation magnetizations Ms, magnetic ordering temperatures Tc, spin-reorientation temperatures Tsr, and anisotropy fields were determined. Pr2Co14B exhibits a transition between uniaxial and planar anisotropy, with increasing temperature. Partial replacement of Dy or Er for Pr in the Pr2Co14B lattice reduces the observed Tsr and HA values. Substitution with Dy in Pr2−xRxCo14B has a smaller effect than with Er. This behavior is believed to be a consequence of a stronger crystal field interaction in the Dy-substituted systems. All materials investigated were found to absorb about 3.5 hydrogen atoms per formula unit at an applied pressure of 10 atm. Introduction of hydrogen into the alloy expands the lattice, changes the magnetic moment of the system slightly and reduces Tsr and HA significantly. This effect is found to be stronger in the Dy-substituted compounds. The weakening of the 4f-3d exchange interactions relative to crystal field interactions of the 4f ions is considered to be responsible for lowering the anisotropy fields upon hydrogen absorption. The results obtained for the host and the hydrides are discussed in terms of their proposed magnetic phase diagram.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340567
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