A NEUTRON POWDER DIFFRACTION STUDY OF THE STRUCTURE IN Nd2Fe17Nx(x = 2.5, 3.0, 5.5)

The crystallographic and magnetic structures of Nd₂Fe₁₇N_x(x = 2.5, 3.0, 5.5) at room temperature were refined by Rietveld analysis of neutron powder diffraction data. We found that Nd₂Fe₁₇N_x has a Th₂Zn₁₇ type structure (S.G. R3m) and the nitrogen atoms occupy both 9e and 18g sites simultaneously and at different rates.     

POWDER NEUTRON DIFFRACTION STUDIES OF THE CRYSTALLOGRAPHIC AND MAGNETIC STRUCTURE OF Ho2Fe9Ga8 and Ho2Fe9Ga6AI2

The crystallographic and magnetic structures of Ho₂Fe₉Ga₈ and Ho₂Fe₉Ga₆AI₂ were studied by powder neutron diffraction at room temperature. The atom fractional occupancies of Ga and Al and the magnetic moments of Ho and Fe were obtained by using Rietveld analysis program. The magnetic structures of the two samples show an easy-axis anisotropy, with the Fe magnetic moment being ferrimagneticlly coupled to those of Ho.     

MAGNETIC PROPERTIES OF Dy2Fe17-xCrx AND Er2Fe17-xCrx(x=0-3)COMPOUNDS

The crystal structure and magnetic properties of R₂Fe_17-xCr_x(R=Dy,Er,0≤x≤3) compounds have been investigated by me ans of X-ray diffraction and magnetization measurements. These compounds have hexagonal Th₂Ni₁₇-type structure. The unit-cell volumes decrease with the increase of Cr concentration x. The Curie temperature T_c of the Er₂Fe_17-xCr_x compounds increases from 320 K for x=0 to 403 K for x=1.0 and then decreases with further increase of x. The Cur ie temperat ure T_c of Dy₂Fe_17-xCr_x compounds increases from 364 K for x=0 to 435 K for x=1.0 and then decreases with further increase of x. The saturation magnetization of these compounds shows an approximately linear decrease with the increase of x. Spin reorientation transitions occur s in Er₂Fe_17-xCr_x(x=2.0 and 3.0).     

NEUTRON-POWDER-DIFFRACTION STUDY OF THE STRUCTURE AND MAGNETIC PROPERTIES OF Nd2Fe14Si3

The crystal and magnetic structures of Nd₂Fe₁₄Si₃ at room temperature were refined by Rietveld analysis of neutron-powder-diffraction data. It was found that silicon atoms occupy preferentially both 18h and 18f of Th₂Zn₁₇-type structure with occupancies 0.36 and 0.14, respectively, The Fe-Fe bond-lengths computed with the refined crystallographic parameters have optimum values, as compared with those of Nd₂Fe₁₇ compounds, which can explain well why the Curie temperature rises strongly when the unit cell volume reduces with the substitution of silicon for iron in Nd₂Fe₁₇.     

Nd2-xSrxCoO4 (x=1.25,1.33,1.60)体系的物理性质研究

用固相反应法制备了Nd2-xSrxCoO4 ( x = 1.25, 1.33, 1.60) 多晶.X射线衍射结果表明样品没有杂项,且都是四方层状K2NiF4结构[1].电阻率结果表明这组样品在测量温区都是半导体行为.对于x= 1.25和1.33的样品,热电势为正值;而对于x= 1.60的样品,热电势在60K发生了由正到负的转变.所有样品在80K左右零场冷却磁化率有个缓变的最大值,在180K左右场冷和零场冷磁化率发生劈裂,表明在低温下样品存在类自旋玻璃态.我们同时测量了x = 1.25样品在110 K到300 K温区的电子自旋共振谱,发现在居里温度左右存在顺磁相和铁磁相激烈竞争,强烈的轨道-自旋耦合导致了短自旋-晶格驰豫时间使谱线宽化.     

The Influence of Milling Modes on the Structure and Magnetic Properties of (Sm,Ho)2Fe17Nx (x = 0, 2.4) Powder Materials

Technical Physics - The composition, structure, and surface topology of as-cast, homogenized, and nitrogenized alloy based on an intermetallic compound Sm2Fe17 with partial substitution of samarium...     

安康矿一维无公度调制结构的电子衍射研究

用电子衍射方法研究了我国新发现的矿物安康矿(Ba_0.827(Ti_5.827V_2.294Cr_0.053)O₁₆)的一维无公度调制结构。确定了其平均结构属四方晶系,平均结构的晶胞参数为a=10.2?,c=2.96?。沿c方向的调制波长为λ=2.30c。详细分析了安康矿电子衍射花样的特征,讨论了安康矿无公度调制结构的可能机制,提出一个空位-位移型调制结构的模型,并讨论了因位移函数初始位相各处不一而引起的 关键词：     

Y(TiFe)12的中子衍射研究

用中子衍射研究了Y(TiFe)₁₂的晶体结构及其磁的特性。观测到Y(TiFe)₁₂为ThMn₁₂型结构,空间群为14/mmm,Fe和Ti分布在三个不等效的晶位上,且Fe和Ti分别择优占据某些晶位。对所得结果进行了初步讨论。 关键词：     

FORMATION AND MAGNETIC PROPERTIES OF Dy2Fe17-xMnxC(x = 0-17) PREPARED BY ARC-MELTING

We report on alloys formed by replacing iron with manganese in the compound Dy₂Fe₁₇C_1.0 Samples were characterized by X-ray diffraction and magnetic measure-ments, The 2:17-type structure can be crystallized in the whole range of manganese substitution. The Curie temperature of the series of Dy₂Fe_17-xMn_xC_1.0(x= 0-17) drops down considerably from 515K for x = 0 to about 20K for compounds with high manganese concentration, and the compensation point was observed in a narrow range of x≈4-6. The rapid decrease of the magnetization shows that the manganese substitution is not a simple magnetic dilution to the transition-metal sublattice mo-ment, it indicates that the moment of Mn may be antiparallel to that of Fe. The field dependence of the magnetization of Dy₂Fe_17-xMn_xC_1.0 may indicate the existence of the nonlinear magnetic structure for the samples with high Mn conoentrations.     

Nd(Fe,Si)11Cx化合物的全电子计算(x=0,2)

采用基于第一原理的全势能线性缀加平面波加局域轨道((L)APW lo)方法对Nd(Fe,Si)11Cx化合物(x=0,2)的电子结构进行了计算,得到了化合物态密度和磁矩等信息.计算结果表明NdFe9Si2化合物中Si原子主要与4b和32i位Fe原子产生杂化,导致Fe原子磁矩减小.NdFe9Si2C2化合物C原子使32i位Fe原子磁矩进一步降低,同时减弱了Si原子的影响,使得4b位Fe原子磁矩增大.     

μ+ shift study inCdMgx (x=1%, 2%, 2.5%)shift study inCdMgx (x=1%, 2%, 2.5%)

In continuation of our earlier studies of the anomalous temperature dependence of the μ⁺ Knight shift K_μ in Cd,CdHg (1.2 at %) andCdMg (3.38 at %) — interpreted as due to Van Hove-type singularities in the local density of electron states /1/ — we have studied the temperature dependence of the μ⁺ Knight shift in polycrystallineCdMg (1.04 at %, 2.05 at %) and in a single crystal ofCdMg (2.5 at %). In contrast to pure Cd no anisotropies in K_μ could be detected. The temperature dependence of K_μ in aCdMg (2.05 at %) sample and in the monocrystallineCdMg (2.5 at %) sample essentially reproduces the one previously observed in polycrystallineCdMg (3.38 at %), showing a steplike discontinuity and a logarithmic singularity. A complete different behaviour is observed inCdMg (1.04 at %), where no logarithmic singularity seems to show up and where a steplike discontinuity of opposite sign at around 90 K is clearly seen. If these singularities are still to be interpreted in terms of Van Hove singularities, the question arises why there is such a nonlinear dependence on the Mg concentration.     

Magnetic and57Fe Mössbauer studies of intermetallic compounds R2 (Fe1−x−y Ni x Co y )17 (R=Y,Gd,Tb,x=0,0.10, 0.20,y=0,0.05, 0.10)

Mössbauer studies of R₂(Fe_1?x?y Ni _x Co _y )₁₇ showed that the transferred hyperfine field at Fe nuclei due to magnetic rare earth (R) atoms is about one Tesla. Magnetic moments of the R atoms were determined from magnetic measurements as μTb=8.52μB, μGd=6.22μB. The mixed substitution of Ni and Co for Fe leads to an increase of the ordering temperature. A slight preference occupancy for Fe was observed involving the dumbbell shaped f or c site. The substitution effects of Ni and Co on the hyperfine field of f or c site, the average hyperfine field and the average isomer shift were also discussed.     

ZnS(111)表面电子结构研究

利用Ｍｕｆｉｎ-Ｔｉｎ轨道线性组合（ＬＭＴＯ）法，采用ｓｌａｂ模型计算了半导体ＺｎＳ（１１１）表面的电子结构，给出了总体、局域及分波态密度，分析了两种ｓｌａｂ模型的表面稳定性和表面态．理论态密度曲线与ＺｎＳ（１１１）表面同步辐射光电子能谱相符合     

一硼化物和二硼化物超导体电子结构研究

本文使用准确的第一原理方法,对一硼化物和二硼化物超导体进行了电子结构研究,从而发现硼化物超导体所具有特殊的电子结构属性.     

Y(Co1-xCux)5中子衍射研究

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K2H(IO3)2Cl单晶中子衍射结构分析

利用中子四圆衍射仪收集了K₂H(IO₃)₂Cl单晶的衍射数据共481个,其中独立衍射351个。利用SHELX程序做了Fourier合成及差值Fourrer合成,并用ORXFLS4程序做了最小二乘法修正(其中包括各向同性及各向异性消光修正),R因子达到3.3％,确定了结构中氢原子的位置,肯定了氢键的存在。 关键词：     

激光束在LiNbO3:Fe晶体中的异常衍射现象(Ⅱ)——o光入e光出的衍射

本文首先叙述了一些o光入e光出衍射的实验现象,包括衍射图样随温度的变化以及相应的Kaman光谱的变化等。然后用文献[1]中的方法,对室温衍射图样进行了计算。证明这种偏振面旋转90°的异常衍射现象是空间相位光栅的各向异性衍射产生的。对一些其它实验现象也作了解释。 关键词：     

激光束在LiNbO3:Fe晶体中的异常衍射现象(Ⅰ)——e光入e光出的衍射

根据的相位光栅各向异性衍射理论,应用顾世杰、李荫远发展的方法,对于激光束在厚的LiNbO₃:Fe晶体(厚度≈1cm)中的异常衍射现象作了计算。如果晶体中被照射后有无规的电荷富集分布,则Fourier分解后可得到无穷个相位光栅,衍射图形决定于光栅的衍射效率。计算结果表明,对e光入e光出的衍射图形,可以解释中央光斑(由透镜效应所决定)两边的光瓣。结果与实验基本符合。 关键词：     

Mössbauer spectrometric study of ternary Sm2Fe17Nx(x>3)

Among the ternary rare earth-iron-nitrogen compounds, Sm₂Fe₁₇N_x, invented and refined by Asahi Chemical Industry Co., Ltd., shows high magnetic anisotropy, intrinsic coercivity and high saturation magnetization. Powders of Sm₂Fe₁₇, prepared by are melting method, were nitrided in a mixed gas of hydrogen and ammonia to get x=0≈8 samples /1.2/. These samples have crystal structure of Th₂Zn₁₇ and Fe atoms are estimated to locate in 6c, 9d, 18f, and 18h sites /2.3/. The Mossbauer spectrum of Sm₂Fe₁₇N_{3. z} showed several unique magnetic properties. For example, Q.S. due to Fe occupying 18h site shifted to the direction of minus velocity. The result indicates that the nitrogen sites are not only 9e but 3b. CEM spectra of Sm₂Fe₁₇N_x powders showed the doublet due to iron oxide indicating that the surface of Sm₂Fe₁₇N_x powders were oxidised /4/. but even if they were exposed to strongly oxidative atmosphere, the thickness of the oxidised layers increased little, resulting no effect to the magnetic properties and to the Mossbauer magnetic parameters of the bulk.     

Thermal dissociation of intercalated titanium selenides Fe x TiSe2 (x = 0.10, 0.25, 0.50)

Using static tensimetry, the selenium pressure during dissociation of intercalated compounds Fe _x TiSe₂ has been measured in a temperature range of stability of the homogeneous material and in the region of decomposition caused by thermal expansion of the polaron band. It has been shown that covalent centers in the stability region of the homogeneous state, which are stabilized by the polaron state of conduction electrons, behave as the effective oxidants lowering the Fermi level. Broadening of the polaron band in the region of a high iron concentration leads to weakening the oxidizing influence of polarons. Iron selenides are formed during the decomposition of intercalated compounds, which leads to an essential non-quasi-binarity of the Fe-TiSe₂ system.