X.R. Wang
材料科学技术（英文）
This paper has constructed two kinds of atomic and electronic models for hexagonal β-Mo2C and orthorhombic α-Mo2C. The optimized lattice parameters, elastic constant matrixes and overlap population for Mo2C crystal cells have been obtained to realize the characterization of the hardness and melting point of the two structures by the first-principles plane wave pseudo potential method based on the density functional theory. The results reveal that the calculated lattice parameters of the Mo2C crystal cells agree with the experimental and other calculated data. The calculated melting point/hardness are 2715 K/11.38 GPa for β-Mo2C and 2699 K/10.57~12.67 GPa for α-Mo2C, respectively. The calculated results from the density of states (DOS) demonstrate that the hybridization effect between Mo-3d and C-2p states in α-Mo2C crystal cell is much
stronger than that in β-Mo2C one.
关键词:
First-principle; Mo2C
YANG Jilian ZHANC Baisheng DINC Yongfan China Institute of Atomic Engergy
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Beijing
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ChinaYANG Yingchang ZHANG Xiaodong Peking University
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Beijing
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ChinaPAN Shuming General Research Institute for Non-Ferrous Metals
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Beijing
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China associate professor
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P.O.Box 275
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Branch No.30
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Beijing 102413
,
China
金属学报(英文版)
The N occupying sites and magnetic structures in R_2Fe_(17)N_x(R=Y,Dy,Nd)are de- termined by neutron diffraction.The effects of the site occupation of N on magnetic properties are discussed primarily.
关键词:
neutron diffraction
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null
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null
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null
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null
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null
杨继廉
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张百生
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丁永凡
,
杨应昌
,
张晓东
,
潘树明
金属学报
用中子衍射法测定了R_2Fe_(17)N_x(R=Y,Dy,Nd)中N的占位及磁结构,初步讨论了N的占位对磁性能的影响
关键词:
中子衍射
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Curie temperature
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permanent magnet
Journal of Physics-Condensed Matter
In this study, the transport and magnetic properties of electron-doped perovskites R(x)Ca(1-x)MnO(3) (R = La, Y and Ce) were investigated. As the R ion content increases, the crystal structure, resistivity, magnetoresistance, magnetization and related characteristic temperature of these systems all vary systematically. The data show that the variations in the electrical transport properties are mainly dependent on carrier concentration, whereas the magnetic properties of these systems are also dependent on crystal structure. When the carrier concentration exceeds a certain level, charge ordering occurs, leading to the localized electronic state and peaks in the magnetization curves. The magnetic transition temperature T(N) can be well described by crystal structural parameters, suggesting that crystal structure and magnetic properties are strongly coupled to each other.
关键词:
rare-earth manganates;phase-separation;colossal magnetoresistance;manganites;oxides;bandwidth;physics;camno3;ln
Journal of Applied Physics
In Ho2Fe14B and Ho2Fe14C the temperature dependence of the ac initial susceptibility between 4.2 and 300 K shows two peaks. The peak at the lower temperature can be explained by a well-known spin reorientation transition (at 62 K for Ho2Fe14B and at 40 K for Ho2Fe14C). The peak at the higher temperature (at 245 K for Ho2Fe14B and at 265 K for Ho2Fe14C) disappears when the external field is applied parallel or perpendicular to the preferential direction of a magnetically aligned sample. The similar peak was also traced for R2Fe14X compounds (R = Sm, Tb, Dy, Ho, Er, and Tm; X = B or C). Searching for the nature of this peak traced by measuring the temperature dependence of the ac susceptibility for 3d-4f compounds is still under progress.
关键词:
Journal of Applied Physics
The effect of Co substitution on structure, phase transformation, and magnetic properties of R(16)Fe(76-x)Co(x)C(8) (R equivalent to Nd, Dy; 0 <= x <= 76) alloys prepared by a remilling process has been studied systematically. The process of remilling and subsequent annealing is more beneficial for the formation of Nd(2)(Fe,Co)(14)C compound in Nd(16)Fe(76-x)Co(x)C(8) alloys than in Dy(16)Fe(76-x)Co(x)C(8) alloys. The R(2)(Fe,Co)(14)C phase is obtained for Nd(16)Fe(76-x)Co(x)C(8) alloys with 0 <= x <= 20 and Dy(16)Fe(76-x)Co(x)C(8) alloys with 0 <= x <= 25. Higher Co content results in the formation of Nd(2)(Fe,Co)(17)C(delta)-type phase and Dy(Fe,Co)(7) phase for Nd(16)Fe(76-x)Co(x)C(8) and Dy(16)Fe(76-x)Co(x)C(8) alloys, respectively. The high coercivity, (i)H(c)=48.5 kOe, is achieved for Dy(16)Fe(51)Co(25)C(8) alloy. (C) 2008 American Institute of Physics.
关键词:
permanent-magnets;r2fe14c;carbides;carbon
WANG Bowen
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WU Changheng
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ZHUANG Yuzhi
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JIN Ximei
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LI Jingyuan(Institute of Metal Research
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Chinese Academy of Sciences
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Shenyang 110015
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China)(Shenyang Institute of Technology
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Shenyang 110023
,
China)(Institute of Physics
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Chinese Academy of Sciences
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Beijing 100080
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China)
金属学报(英文版)
The structure and magnetostriction of R(Fe_(1-x)Al_x)_y alloys(R=Dy_(0.65)Tb_(0.25)Pr_(0.1),x≤0.3,y=1.8 and 2) have been investigated using metallography, X-ray diffraction, electron probe micro- analysis(EPMA) and standard strain gauge techniques.It was found that the matrix of R(Fe_(1-x)Al_x)_2 alloys is cubic Laves phase(Dy,Tb,Pr)(Fe,Al)_2 and the second phase is PuNi3-type (Dy,Tb,Pr)(Fe,Al)_3 when x<0.15.The R(Fe_(1-x)Al_x)_(1.8) alloys contain trace of rare earth-rich phase.The magnetostriction of R(Fe_(1-x)Al_x)_y alloys decreases with increasing x in high magnetic fields; however, it exhibits a peak when x = 0.05 in low magnetic fields(H≤ 160 kA / m).The magnetostriction of R(Fe_(1-x)Al_x)_(1.8) alloys is higher than that of R(Fe_(1-x)Al_x)_2 alloys when x<0.15.
关键词:
:rare earth-iron alloy
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null
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null
Journal of Magnetism and Magnetic Materials
The structure and magnetostriction of preferentially oriented polycrystalline R(Fe0.95Al0.05), alloys (R = Dy0.65Tb0.25 Pr-0.1, 1.80 less than or equal to x less than or equal to 1.95) prepared by Czochralski technique, have been investigated using optical and SEM metallography, X-ray diffraction, transmission electron microscopy and standard strain gauge techniques. The alloy contains some rare earth-rich phase when x less than or equal to 1.85, however (Dy,Tb,Pr)(Fe,Al)(3) particles emerges when x > 1.85, the amount of which increases with increasing x. X-ray diffraction analysis indicated that almost all crystallites grow along [110] direction when x less than or equal to 1.85 whereas part of crystallites grows along [112] direction when x greater than or equal to 1.90. The magnetostriction along the growth direction of the samples has been assessed.
关键词:
magnetostriction;cubic Laves phase pseudobinary compounds;iron-aluminum compounds;crystals
Journal of Magnetism and Magnetic Materials
Structure, Curie temperature and magnetostriction of RFex (1.6 less than or equal to x less than or equal to 2.0) and R(Fe1-yTiy)(1.8) (y less than or equal to 0.2) alloys (R = Dy0.65Tb0.25Pr0.1) have been investigated using optical microscopy, X-ray diffraction, AC initial susceptibility and standard strain gauge techniques. The homogenized RFe, alloys are found to be essentially single phase in the range of 1.8 less than or equal to x < 1.85. The second phase is a rare-earth-rich phase when x < 1.8, and (Dy, Tb, Pr)Fe-3 phase when x greater than or equal to 1.85. X-ray diffraction indicates that the R(Fe1-yTiy)(1.8) alloys contain a small amount of Fe2Ti phase when y greater than or equal to 0.05, which increases with the increment of Ti content. The Curie temperature of R(Fe1-yTiy)(1.8) alloys slightly enhances with increasing Ti concentration when y less than or equal to 0.05, then remains almost unchanged in the range of 0.05 < y less than or equal to 0.20. The magnetostriction of RFex alloys is improved when x less than or equal to 1.80 and reduced by increasing Fe content when x greater than or equal to 1.85. The magnetostriction of R(Fe1-yTiy)(1.8) alloys is lowered by increasing Ti content.
关键词:
rare earth iron compounds;substitution effects;laves phase;magnetostriction
