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  • 1995-1999  (2)
  • 1990-1994  (5)
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  • 1
    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
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5559-5561 
    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
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4978-4980 
    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
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  • 4
    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
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  • 5
    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
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6262-6264 
    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
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6289-6289 
    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
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