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  • 1
    Electronic Resource
    Electronic Resource
    Investigation of Pr-Fe-B magnets with high performance (abstract) : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6289-6289 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pr-Fe-B magnets with high performance based on 2:14:1 structure were investigated. The effect of fabricating processes on the oxygen content and on the magnetic properties was studied. The coercivity iHc decreases, but the Br and (BH)max of the magnets increase with the decrease of the Pr content. The decrease in the α-Fe content of the alloys annealed at 1000 °C for more than 360 h results in the enhancement of the magnetic properties of the magnets. Under the optimum conditions, the magnetic properties for Pr14Fe79.5B6.5 magnets are found to be iHc=656 kA/m, Br=1.42 T, (BH)max=374 kJ/m3. The microstructures of the magnets were investigated. The effect of the secondary phases in the grain boundary on the coercivity of the magnets was studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355427
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of cobalt substitution on magnetic properties of R2Fe17 silicides (R=Y, Gd, Tb, Er, and Tm) : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6262-6264 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic characteristics and unit-cell dimensions of the (off-stoichiometric) R2Fe17-type alloys based on R2Fe14−xCoxSi2, where R=Gd, Tb, Er, Tm, and Y and x=4 were determined. Partial substitution of Fe by Co slightly increases the saturation magnetization of the alloys and produces an average increase in the Curie temperature (Tc) of 55 K per Co atom. The enhancement of the Curie temperature with the addition of cobalt is attributed to the strengthening of the average 3d-3d exchange interaction. For Er- and Tm-containing compounds, replacement of Fe by Co has a remarkable effect in shifting the observed spin reorientation temperature toward higher temperatures. These results are discussed in terms of the influence of the interaction of the 4f electrons of the rare-earth ions with the 3d electrons of the transition-metal ions, which modifies the overall anisotropy of the alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355418
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  • 3
    Electronic Resource
    Electronic Resource
    Quantitative characterization of additional ferromagnetic phase in melt-quenched and sintered Nd–Fe–B-based magnets : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5513-5515 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantitative evidence of a ferromagnetic Fe-rich minor phase present in both melt-quenched/die-upset and sintered magnets based on the Nd2Fe14B composition is presented. Full hysteresis loops were obtained at elevated temperatures (650 K≤T≤800 K) and were subsequently decomposed to obtain the saturation magnetization Ms of the minor phase as well as the paramagnetic slope of the 2-14-1 major phase as a function of temperature. Assuming a composition of pure iron, the calculated volume % of the impurity phase in the die-upset magnets is consistent with that obtained from previous observations of the widths and geometry of the intergranular phase found in the same magnets. The magnetization of the ferromagnetic impurity phase in the melt-quenched magnets decreases more rapidly than that of pure iron; extrapolation indicates a Curie temperature in the range 925 K≤T≤975 K. The paramagnetic susceptibility of the Nd2Fe14B main phases exhibits Curie–Weiss behavior with the same paramagnetic Curie temperature for both sintered and die-upset samples. The Curie constants differ, however, probably due to the different degrees of crystallographic alignment. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362295
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic and crystallographic properties of R2Fe14Si2 (R=Y, Gd, Dy, Er, and Tm) compounds (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6334-6334 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In connection with a previous work, magnetic and crystallographic properties of the off-stoichiometric compounds R2Fe14Si2 of the R2Fe17-type are studied. Magnetization curves at T=5 K are observed in a high magnetic field up to 15 T for loose powders as well as for field-aligned powders of the samples expressed in the title. Temperature dependencies of the spontaneous magnetizations are also determined in the temperature region from 5 K to the respective Curie temperature. Detailed x-ray analysis is carried out for Y2Fe14Si2. Conclusions are as follows: (1) the Si substitution brings about significant displacements of the 12j-site Fe as well as the dumbell-site Fe from their original positions, which is discussed in connection with other present experimental data such as the remarkable enhancement of the Curie temperature caused by the Si substitution; (2) averaged Fe moment reduction is strictly determined for the present samples; (3) all the samples have a planer anisotropy at room temperature, taking this fact the magnetization curves for the field-aligned samples are analyzed; (4) exchange interaction between R sublattice and Fe sublattice has been determined for all the samples. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362442
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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Crystal structure and magnetic characteristics of alloys based on R-Fe-Si (R=Y, Nd, Gd, Dy, Ho, Er) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6272-6274 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Crystal structure and magnetic properties of ternary compounds based on R2Fe14Si2 (off-stoichiometric R2Fe17 type) were investigated. Results of the powder x-ray-diffraction indicated that the compounds examined in this study crystallize in the rhombohedral Th2Zn17-type structure when R is Nd or Gd and in the hexagonal Th2Ni17-type when R is Y, Dy, Ho, or Er. The Curie temperature TC and room-temperature saturation magnetization Ms of R2Fe14Si2 system range from 465 to 572 K and 65 to 150 emu/g, respectively. The behavior of TC is found to follow the root of the de Gennes function and can therefore be ascribed to the strength of the rare-earth–iron exchange interaction. The average magnetic moment of Fe in R2Fe14Si2 is estimated to be approximately 2.0 μB at 77 K. Addition of Si in the binary R-Fe lattice induced a large uniaxial magnetic anisotropy at room temperature in some alloys. Results of M vs T for Er2Fe14Si2 indicate a spin reorientation transition at about 100 and 35 K. Dy2Fe14Si2 and Ho2Fe14Si2 exhibit a remarkable magnetic hardening at low temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352667
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of partial substitution of Tb on the spin reorientation of the Er2−xTbxFe14B system : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5559-5561 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerous articles have been published concerning spin reorientation in R2Fe14B (R=rare earth) compounds. Previous measurements have suggested the presence of axial, conical, and planar regions in the magnetic phase diagrams. In the present systems the magnetization versus temperature (10–300 K) has been measured for aligned Er2−xTbxFe14B samples for x=0, 0.2, 0.5, and 1.5 in applied fields of 0–15 kOe. Transitions were determined from the inflection point as obtained from the derivative of the magnetization versus temperature. Earlier theoretical predictions of the magnetic phase diagrams for Er1.8Tb0.2Fe14B indicate that both plane-to-cone and cone-to-axis transitions should be present. Spin reorientations were observed at 194 K for plane to cone and at 212 K for cone to axis, in agreement with the predicted values. There was a weak-field dependence in the transition temperatures, and the strength of the transitions steadily decreased with increasing field. In the case of Er1.5Tb0.5Fe14B, a cone-to-axis spin reorientation was observed at 78 K, again in agreement with the predicted value. Er0.5Tb1.5Fe14B was axial through the 10–290-K temperature range. Thermal hysteretic effects for the transition temperatures were observed upon heating and cooling in an applied field. Detailed results of the spin reorientation for Er2−xTbxFe14B are discussed in terms of the second-order crystal-field effect and exchange interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347949
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetic properties of LaCo13-based systems (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4978-4980 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Four polycomponent systems based on LaCo13 have been studied: La(Co1−xFex)13, La(Co1−xAlx)13, La(Co1−x−yFexAly)13, and La0.7Nd0.3(Co0.7Fe0.3)13. These 1:13 systems were studied because of their potential for permanent magnet fabrication. LaCo13 has a high 3d metal content, the highest for any known rare-earth intermetallic, a 13 kG saturation induction, and a high Tc (1318 K). Unfortunately, it is cubic and lacks anisotropy. The substituted systems were examined as a portion of a program to find LaCo13-based systems of applications significance. Replacement of Co in LaCo13 by Fe and/or Al leads to a rapid decline in Tc for all systems studied. Replacement of Co by Al results in a decline in moment, whereas replacement by Fe leads to a rise in moment to 2.39μB/3d atom for La(Co0.4Fe0.6)13, as compared to 2.46μB/3d atom for Fe0.7Co0.3. Analysis of the magnetic data shows that vacancies occur in both half-bands for LaCo13 (4.8 spin up and 3.24 spin down) but in only one half-band in La(Co1−xAlx)13 for x≥0.2. Nd in these systems carries a moment of 3μB, close to that of the free tripositive ion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344695
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