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讨论了利用分子场近似结合中子衍射或X射线衍射的实验结果计算R2Fe17型稀土过渡族化合物中稀土磁矩与过渡族磁矩之间交换耦合常量的方法,并据此计算了R2Fe17-xAlx(R=Tb,Dy,Ho,Er,Gd,x=7或8)化合物中稀土磁矩与过渡族磁矩之间的交换耦合常量.计算结果与实验值符合较好.
关键词:
2Fe17-xAlx化合物')" href="#">R2Fe17-xAlx化合物
交换耦合常量 相似文献
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Haiying Chen Yan ZhangJingzhi Han Honglin DuChangsheng Wang Yingchang Yang 《Journal of magnetism and magnetic materials》2008
A series of R2Fe17 (R=Sm, Gd, Tb, Dy, Er) have been synthesized. The magnetocaloric effect (MCE) of these compounds has been investigated by means of magnetic measurements in the vicinity of their Curie temperature. The Curie temperature of Er2Fe17 is 294 K. The maximum magnetic entropy change of Er2Fe17 under 5 T magnetic field is ∼3.68 J/kg K. In the R2Fe17 (R=Sm, Gd, Tb, Dy, Er) system, the maximum magnetic entropy change under 1.5 T magnetic field is 1.72, 0.89, 1.32, 1.59, 1.68 J/kg K corresponding to their Curie temperature (400, 472, 415, 364, 294 K), respectively. 相似文献
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We found that the nitrogen atoms can enter into the R2Fe14B structure by a proper heat treatment in nitrogen atmosphere. The crystallographic structure and magnetic properties of R2Fe14BNx, R =Nd and Y, have been investigated by using X-ray and neutron diffraction techniques as well as magnetic measurements. The neutron diffrac-tion data show that the nitrogen atoms occupy the 4f interstices. The interstitial nitrogen atoms were found to have an effect of enhancing Curie temerature, whereas, decreasing saturation magnetization and magneto-crystalline anisotropy. The rela-tionship of the crystal structure and the intrinsic magnetic properties of this crystal is discussed. 相似文献
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S. Sinnema R.J. Radwanski J.J.M. Franse D.B. de Mooij K.H.J. Buschow 《Journal of magnetism and magnetic materials》1984,44(3):333-341
Ternary tetragonal compounds of the composition R2Fe14B were observed for R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. The lattice constants and the X-ray density of these compounds were determined. Also determined were the magnetic properties, comprising the temperature dependence of the magnetization in the range 4.2–700 K and the field dependence of the magnetization at 4.2 K in fields up to 20 T. These latter measurements were made in two mutually perpendicular directions, making it possible to determine the anisotropy fields. The magnetocrystalline anisotropy was found to consist of contributions due to the Fe and rare-earth sublattice, respectively. 相似文献
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The magnetic properties of Y2Fe17−xGax for 3≤x≤7 and Gd2Fe17−xGax for 5≤x≤7 have been investigated using 57Fe Mössbauer spectroscopy. These compounds have the rhombohedral Th2Zn17 structure. X-ray diffraction analysis of aligned powders shows that the easy direction of magnetization is parallel to the c-axis in Y2Fe10Ga7 and Gd2Fe10Ga7 and is perpendicular to the c-axis in Y2Fe14Ga3, Y2Fe12Ga5, Gd2Fe12Ga5 and Gd2Fe11Ga6. Mössbauer studies indicate that those samples are ordered ferromagnetically. The 57Fe hyperfine field decreases with increasing Ga content. This decrease results from the decreased magnetic exchange interactions resulting from Ga substitution. The average isomer shift, δ, for R2Fe17−xGax (R=Y and Gd) at room temperature is positive and the magnitude of δ increases with increasing Ga content. 相似文献
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A systematic investigation of nitrides R3Fe29-xCrxN4(R=Y, Ce, Nd, Sm, Gd, Tb, and Dy) has been performed. The nitrogen concentration in the nitride R3Fe29-xCrxNy was determined to be y=4. Nitrogenation leads to a relative volume expansion of about 5.3%. The lattice constants and unit cell volume decrease with in creasing rare earth atomic number from Nd to Dy, reflecting the lanthanide contraction. In average, the increase of Curie temperature upon nitrogenation is about 200 K, compared with its parent compound. The nitrogenation also results in a remarkable improvement in the saturation magnetization and anisotropy fields for R3Fe29-xCrxN4 at 4.2 K and room temperature, comp ared with their parent compounds. A spin reorientation of Nd3Fe24.5 Cr4.5N4 occurs at around 368 K, which is 138 K higher than that of Nd3Fe24.5Cr4.5.Magnetohistory effects of R3Fe29-xCrxN4(R=Nd and Sm) are observed in a low field of 0.04 T. First order magneti zation process occurs in Sm3Fe24.0Cr5.0N4 in magnetic fields of around 3.0 T at 4.2 K. After nitrogenation the easy magnetization direction of Sm3Fe24.0Cr5.0 is changed from the easy cone structure to the uniaxial. The excellent intrinsic magnetic properties of Sm3Fe24.0Cr5.0N4 make this compound a hopeful candidate for new high performance permanent magnets. 相似文献
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D. Sanavi Khoshnoud F. Pourarian 《Journal of magnetism and magnetic materials》2009,321(23):3847-3853
The magnetostriction of the off-stoichiometric R2Fe17-type intermetallic compounds based on R2Fe14−xCoxSi2 (R=Y, Er, Tm and x=0, 4) was measured, using the strain gauge method in the temperature range 77-460 K under applied magnetic fields up to 1.5 T. All compounds show sign change and reduction in magnetostriction values compared to the R2Fe17 compounds by Si substitution. For Y2Fe14Si2 and Er2Fe14Si2, saturation behaviour is observed near magnetic ordering temperature (TC), whereas for Tm2Fe14Si2, saturation starts from T>143 K. Also, Co substitution has different effects on the magnetostriction of R2Fe14Si2 compounds. In Er2Fe10Co4Si2 and Tm2Fe10Co4Si2, saturation occurs below the spin reorientation temperature (TSR). In addition, in Er2Fe14Si2, a sign change occurs in the anisotropic magnetostriction (Δλ) as well as the volume magnetostriction (ΔV/V) at their TSR values. The volume magnetostrictions of the Tm-containing compounds show an anomaly around their TSR. In R2Fe14Si2 compounds, parastrictive behaviour is also observed in ΔV/V near their TC values. In addition, the magnetostriction of the sublattices is investigated. Results show that in R2Fe14Si2 compounds, the rare-earth sublattice contribution to magnetostriction is negative and comparable to the iron sublattice, whereas, in R2Fe10Co4Si2 compounds, the rare-earth sublattice contribution is positive and larger than Fe sublattice. These results are discussed based on the effect of Si and Co substitutions on the anisotropy field of these compounds. Influence of the spin reorientation transition on the magnetostriction of these compounds is discussed in terms of the anisotropic sublattice interactions. 相似文献
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E.B.Guedes de Sousa M.A. Sá J.F.D. Montenegro J.M.Machado da Silva D. Melville 《Solid State Communications》1984,49(9):853-854
Heat capacity measurements of the alloy Pr2(Co0.8Fe0.2)17 in the temperature range 182.5–190.5 K show an anomaly around 188 K. This is associated with a rotation of the magnetization vector from the basal plane to the hexagonal c-axis. 相似文献
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The magnetic properties (magnetic ordering temperature, magnetization) of the ferrimagnetic compounds R
2Fe17 and RFe11Ti, as well as of their hydrides and nitrides, were studied. The hydrogenation-and nitrogenation-induced variation of the
exchange fields acting on the rare-earth (RE) ions from both the Fe sublattice and other RE ions was determined, and the dependence of the Curie temperatures of the starting compounds, their hydrides, and nitrides
on the de Gennes factor was revealed. It was found that incorporation of light atoms (H, N) into the crystal lattices of RFe11Ti and R
2Fe17 increases the Curie temperature T
C substantially, increases the Fe-Fe exchange coupling, and decreases the R-R exchange interactions, as well as increases the R-Fe intersublattice exchange under hydrogenation and decreases it under nitrogenation, an effect that can be understood as
resulting from the attendant changes in the electronic structure of these compounds and in the indirect exchange interactions.
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Translated from Fizika Tverdogo Tela, Vol. 45, No. 10, 2003, pp. 1850–1856.
Original Russian Text Copyright ? 2003 by Nikitin, Tereshina. 相似文献
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Structure and magnetic properties of a new single-molecule magnet [Mn11Fe1O12 (CH3COO)16(H2O)4].2CH3COOH.4H2O 下载免费PDF全文
A new single-molecule magnet [Mn11Fe1O12 (CH3COO)16(H2O)4]?2CH3COOH?4H2O (Mn11Fe1) has been synthesized.The structure has been studied by the single crystal x-ray diffraction. The difference of Jahn--Teller distortion between Fe3+ and Mn3+ ion reveals that Fe3+ ion substitutes for Mn3+ ion on the Mn(3)
sites in the Mn12 skeleton. The temperature dependence of the magnetization gives a blocking temperature TB=1.9K for Mn11Fe1. Based on the magnetization process analysis of the crystal at T=2K, we suggest that Mn11Fe1 has the ground state with a total spin S= 11/2. 相似文献
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The structural stability of the intermetallic compounds R2Co17 and R2Co17T (T=Be, C) is tested by many means including random atom shifts, global deformations and high temperature disturbances under the control of the pair potentials. The structure type and crystal constants of R2Co17 and R2Co17Be are close to experimental results. The addition of Be and C in the interstice of R2Co17 causes a decrease of the cohesive energy, and Be and C only occupies the 9e interstitial site with the Th2Zn17-type structure or the 6h interstitial site with the Th2Ni17-type structure. All the above results indicate that the potentials are valid for studying the structural properties of these kinds of anisotropy materials. 相似文献
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Hydrogen absorption in the cubic compound Lu6Fe23 () leads to a ternary hydride of the composition Lu6Fe23H8 (). The H2 take-up causes a slight increase in the saturation magnetization corresponding to an increase in Fe moment from 1.54 /uB to 1.64/uB per atom. The hydrogen absorption did not lead to a substantial change in the linewidth of the 57Fe Mössbauer spectrum. On the basis of the Mössbauer data it was inferred that the H atoms occupy the f-type interstitial holes characterized by a tetrahedron formed of three Lu atoms and one Fe atom. The decrease in hyperfine field upon charging was correlated with an increase in Curie temperature. 相似文献
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Fully dense nanocomposite magnets containing hard R2Fe14B and soft α-Fe phases were produced from both melt-spun and mechanically milled alloys by hot pressing and subsequent die upsetting. Although R-lean R–Fe–B alloys that do not contain the grain-boundary R-rich phase are known not to be susceptible to texture development by means of die upsetting, we found that small additions of Cu make the texturing possible. The resulting microstructure of oriented platelet grains is similar to that of the R-rich die-upset magnets. Properties of the Cu-containing R2Fe14B/α-Fe die-upset magnets can be further improved by adding Ga. The anisotropic Pr12Fe80Cu1Ga1B6 magnet made from mechanically milled alloy and containing 17.2 wt% α-Fe had a remanence of 13 kG and a maximum energy product of 23.4 MG Oe. The Pr11.25Fe80.75Cu1Ga1B6 magnet made from melt-spun alloy and containing 16.2 wt% α-Fe had a maximum energy product of 19.9 MG Oe. The low coercivity of 3–4 kOe typical for the Cu-containing R2Fe14B/α-Fe die-upset magnets is due to the relatively coarse α-Fe grains. The latter grains are too large for intergranular exchange interaction, but, nevertheless, they are well coupled with the R2Fe14B grains by a long-range magnetostatic interaction. 相似文献