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15 Aug 2001

Volume 90, Issue 4, pp. 1683-2051

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Formation, structural and magnetic properties of Gd3(Co,Cr)29 compounds

W. Q. Wang, J. L. Wang, N. Tang, G. H. Wu, F. M. Yang, and H. M. Jin

J. Appl. Phys. 90, 1920 (2001); http://dx.doi.org/10.1063/1.1388164 (4 pages) | Cited 4 times

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Co-based Gd3Co29−xCrx compounds with a Nd3(Fe,Ti)29-type of structure have been synthesized successfully for x=6.5 and 7.0. The crystal structure and magnetic properties of the Gd3Co29−xCrx compounds have been investigated by x-ray diffraction analysis and magnetic measurements. It has been found that Gd3(Co,Cr)29 with x=6.5 and 7.0 are of ferrimagnetic compounds with Curie temperature of 412 K for x=6.5 and 359 K for x=7.0, respectively. Temperature dependence of the magnetization shows a compensation point of the magnetization at the certain temperature below the Curie temperature. The intersublattice molecular field coefficient, nRT, was derived to be 3.3 T f.u./μB for Gd3Co22.5Cr6.5 on the basis of the magnetization curve at the compensation temperature. It is noteworthy that the Gd3(Co,Cr)29 compounds exhibit favorable easy-axis anisotropy in the whole temperature range below Curie temperature. © 2001 American Institute of Physics.
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61.66.Dk Alloys
75.50.Gg Ferrimagnetics
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.-s Critical-point effects, specific heats, short-range order
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy

Intermediate phases in the hydrogen disproportionated state of NdFeB-type powders

G. Yi, J. N. Chapman, D. N. Brown, and I. R. Harris

J. Appl. Phys. 90, 1924 (2001); http://dx.doi.org/10.1063/1.1388166 (7 pages) | Cited 1 time

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Transmission electron microscopy studies have been carried out on partially disproportionated NdFeB-type alloys. A new intermediate magnetic (NIM) phase has been identified. Moreover, the lamella structure which subsequently develops from the tetragonal NIM phase comprises a tetragonal NdFe-containing (IL) phase and α-Fe. The experimental data show strong evidence of a well-defined crystallographic relation between both the NIM and lamella phases and between the IL phase and α-Fe. These observations give insight into how crystallographic texture, and hence anisotropy, can be developed in NdFeB-type powders processed by the hydrogenation, disproportionation, desorption, and recombination route. © 2001 American Institute of Physics.
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81.05.Bx Metals, semimetals, and alloys
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
68.43.Mn Adsorption kinetics
75.30.Gw Magnetic anisotropy
75.50.Ww Permanent magnets
75.50.Bb Fe and its alloys

Crystal structure and magnetic properties of the compound Nd5Co21B4

W. G. Chu, G. H. Rao, H. F. Yang, G. Y. Liu, and J. K. Liang

J. Appl. Phys. 90, 1931 (2001); http://dx.doi.org/10.1063/1.1389082 (3 pages) | Cited 1 time

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A compound Nd5Co21B4 belonging to the series Rm+nCo5m+3nB2n with m=3, n=2 has been synthesized by melt spinning. The crystal structure and magnetic properties of the compound have been studied by means of x-ray diffraction and magnetic measurements. The compound crystallizes in a hexagonal structure with space group P6/mmm. The Curie temperature, the saturation moment, and the planar anisotropy field of the compound are 570 K, 31.1 μB/f.u., and 861 kOe, respectively. © 2001 American Institute of Physics.
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61.66.Dk Alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Cc Other ferromagnetic metals and alloys
75.30.Gw Magnetic anisotropy

Magnetic and conversion electron Mössbauer spectral study of amorphous thin films of DyxFe100−x and Dy20Fe80−yCoy

K. Fleury-Frenette, J. Delwiche, F. Grandjean, D. Vandormael, and Gary J. Long

J. Appl. Phys. 90, 1934 (2001); http://dx.doi.org/10.1063/1.1385574 (7 pages)

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Amorphous thin films of DyxFe100−x and Dy20Fe80−yCoy, with various x and y values and of ∼40 nm thickness, have been prepared by sputtering on polyimide films. Their magnetization curves and the Mössbauer spectra indicate that at 295 K the iron moments are preferentially oriented parallel to the film in Dy2Fe98 and that Dy6Fe94 is paramagnetic. The DyxFe100−x thin films, where x is 17, 20, 24, 29, 32, 35, and 37, show perpendicular magnetic anisotropies and moderate coercive fields of at most 150 kA/m, whereas the Dy20Fe80−yCoy thin films, where y is 8, 13, 16, and 20, thin films show stronger perpendicular anisotropies and larger coercive fields of ∼400 kA/m. The introduction of cobalt into the amorphous thin films increases their coercive field and the perpendicular magnetic anisotropy. The Mössbauer spectra of the DyxFe100−x and Dy20Fe80−yCoy amorphous thin films consist of broadened sextets which have been analyzed with a distribution of hyperfine fields by assuming that the iron moments are oriented perpendicular to the plane of the film. Detailed fits of the Mössbauer spectrum of Dy20Fe80 indicate that the cone angle of the iron magnetic moments cannot be determined with accuracy. The average hyperfine fields in the DyxFe100−x amorphous thin films are smaller than those in the crystalline dysprosium–iron intermetallic compounds. The average hyperfine field increases from ∼140 kOe in the DyxFe100−x films to ∼220 kOe in the Dy20Fe80−yCoy films, an increase which is in agreement with the increase in the saturation magnetization. The x dependence of the isomer shift indicates that there is strong dysprosium–iron bonding, whereas the y dependence of the isomer shift reveals an enhancement of the d-electron localization. From earlier x-ray magnetic circular dichroism results and the Mössbauer spectral results presented herein, iron magnetic moments of 0.87 or 0.67 μB, corresponding to 2.9 or 2.8 holes in the iron 3d band, have been obtained for the DyxFe100−x amorphous thin films with x greater or smaller than 27, respectively. © 2001 American Institute of Physics.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
81.05.Bx Metals, semimetals, and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
76.80.+y Mössbauer effect; other γ-ray spectroscopy
75.30.Gw Magnetic anisotropy
75.30.Cr Saturation moments and magnetic susceptibilities
71.70.Jp Nuclear states and interactions
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