2—三苯基锗基乙基苯基酮,4—三氯锗基—4—甲基—2—戊酮及其类似？…

我们合成有机锗化合物的理要中间体４－三氯锗基－４－甲基－２－戊酮（Ａ）、３－三氯锗基－３,５,５－三甲基环已酮（Ｂ）、２－三氯锗基－２－苯基乙基苯基酮（Ｃ）、２－三苯基锗基乙基苯基酮（Ｄ）,没测量了他们的Ｒａｍａｍ和ＩＲ光谱半进行了讨论。在化合物Ａ－Ｄ的Ｒａｍａｍ和ＩＲ光谱,苯环中的Ｃ－Ｈ伸缩振动,饱和Ｃ－Ｈ伸缩振动,饱和Ｇｅ－Ｃ伸缩振动等特征数据基本一致。Ｃ＝０伸缩振动在Ｒａｍａｍ和ＩＲ光谱中位     

1—苯基—4—乙基（2′—对取代苯基）环己硅烷类液晶化合物？…

运用ＡＭ１和ＰＭ３两种ＳＣＦ－ＭＯ方法,通过能量梯度全优化计算,给出４种１－苯基－４－乙基（２′－对取代苯基）环已硅烷类液晶化合物的稳定几何构型,电子结构和分子的基本性质（生成热,偶极矩等）,联系有机电子结构理论进行了细致的讨论。     

2：17型结构Gd—Fe—Co—Ga化合物的结构与磁性

用电弧熔炼的方法制备了Ｇｄ２（Ｆｅ１－ｘＣｏｘ）１５Ｇａ２（０≤ｘ≤１０）和Ｇｄ２（Ｆｅ０８Ｃｏ０２）１７－ｙＧａｙ（０≤ｙ≤８）化合物，通过Ｘ射线衍射和磁性测量手段研究了它们的结构和磁性．实验结果表明它们都是２∶１７型结构的单相化合物．Ｇｄ２（Ｆｅ１－ｘＣｏｘ）１５Ｇａ２的单胞体积Ｖ随Ｃｏ含量的增加单调下降，而居里温度ＴＣ单调上升，１５Ｋ下的饱和磁化强度Ｍｓ随Ｃｏ含量的增加开始时略有增大，在ｘ＝０２时出现极大值，然后单调下降；对Ｇｄ２（Ｆｅ０８Ｃｏ０２）１７－ｙＧａｙ的样品，随Ｇａ含量的增加单胞体积增加，居里温度和饱和磁化强度单调下降．用Ｃｏ替代Ｆｅ，或用Ｇａ替代Ｆｅ和Ｃｏ都能导致Ｆｅ或Ｃｏ次晶格出现室温单轴各向异性，这可能与Ｇａ原子的择优占位有关．     

Structural and magnetic properties of Dy2Co17—xMnx compounds

Using x-ray diffraction and magnetic measurements, we have studied the structural and magnetic properties of Dy₂Co_17-xMn_x (x=0∽5) compounds with a rhombohedral Th₂Zn₁₇-type structure. With an increasing Mn concentration x, the unit-cell volume V was found to increase linearly. The Curie temperature T_c decreases linearly, and the saturation magnetization M_s at 5K first increases slightly for x<1, then decreases rapidly for x>1 with a further increase of Mn concentration x. In compounds for x=1～3, a spin reorientation was found. A magnetic diagram of the compounds is given.     

Nd—Fe—C（或 BC）三元化合物的晶体结构与磁性

本文中研究了从Nd_(14)Fe_(78)B_8过渡到Nd_(14)Fe_(78)C_8时化合物的晶体结构与内禀磁性。指出轻稀土-Fe-C化合物形成P42/mnm型四方结构的结晶学条件在于适当的热处理温度。在Nd_(14)Fe_(78)B_(8-x)C_x系列中,随着C含量的增加,居里温度略有减少,饱和磁化强度σ_3出现一个平缓的峰值变化,室温下的剩磁σ_r、内禀矫顽力_iH_c和磁晶各向异性场H_a都明显增大。含碳样品的各向异性行为与Nd-Fe-B相似,室温下易磁化方向沿e轴,低温下易轴各向异性转变成易锥型。自旋再取向温度随C的增加逐渐降低,但1.5K下的锥角有轻微的增大,这表明在Nd和Fe次晶格的各向异性之间存在着复杂的耦合。此外,适当富Nd的Nd-Fe-C化合物有强的各向异性。     

（La1—xSrx）2CuO4高Tc单晶样品中Sr对其性质的影响

实验上研究了（Ｌａ１－ｘＳｒｘ）２ＣｕＯ４）高Ｔｃ单晶样品的ｃ－轴正常态电阻同温度的关系以及Ｔｃ附近ｃ－轴电阻作为磁场和磁场取向的函数，结果表明，（１）随着Ｓｒ含量的增加，ｃ－轴正常态电阻从半导体行为变为金属行为，和（２）固有的各向异性随Ｓｒ含量的增加而逐渐变弱，这些意味着Ｓｒ掺杂在Ｌａ基系统中有利于Ｃｕ－Ｏ面间耦合的改善。     

Room—Temperature A1GaAsSb／InGaAsSb Multi—Quantum—Well Lasers with High Chraracteristic Temperature

Planar structure A1GaAsSb/InGaAsSb lasers operated at 2.01/zm with high characteristic temperature have been fabricated from a strained multiple quantum-well heterostructure. To decrease the free carrier induced absorption of optical mode in the mid-infrared, we design a broaden waveguide layer in the laser structures to decrease the optical mode distribution in the heavy doped cladding layer, therefore it can be absorbed easily. To enhance the characteristic temperature of laser diodes, A1 constituent up to 80% was applied to the A1GaAsSb cladding layer. The laser diodes with a threshold current density of 1.8 kA/cm2 can be pulsed operating up to 340 K. The characteristic temperature To is 125 K and 90 K in the operating temperature ranges 170-220 K and 230-340 K, resDectivelv. The emission spectrum shows a multiple longitudinal mode.     

Magnetic Properties and Magnetoresistance Effect of YMn6 Sn6—x Crx （x=0—0.8） Compounds

The magnetic properties and magnetoresistance effect of YMn6Sn6-x Crx(x=0-0.8) compounds have been experimentally studied by magnetic properties and resistivity measurements in the applied field range 0-5T.The compound (x=0.8) displays a ferromagnetic behaviour,while the compounds (x=0-0.4) display an antiferromagnetic behaviour in the whole ordering temperature range.The compounds(x=0.5,0.6) experienced a transition from an antiferromagnetic state to a ferromagnetic state with increasing temperature.The compound with x=0.8 is rapidly saturated in the lower magnetic field with saturation magnetization of 35.92emu/g.The compounds(x=0-0.6) display a field-induced metamagnetic transition,and the threshold fields decrease with increasing Cr content.The cell-volume V of compounds(x=0-0.8) increases,and the ordering temperature decreases with the increasing Cr content.A large magnetoresistance effect was observed for the compounds (x=0.4,0.5),and the maximum absolute value at 5K are 32% and 24% under 5T for x=0.4 and x=0.5,respectively.     

Laser—Surface Interaction of Compound Semiconductors—Desorption Induced by Electronic Excitation of Surface States

In this talk a review is given of currently carricd out studies on laser-induced desorption from surfaces of compound semiconductors.The reviewincludes only the non-thermal processes.which can be detected by eitherirradiation with laser of subgap photon energies or with extremely low-intensity pulsed lasers.It is emphasized also that laser induced non-thermaldesorption is a powerful technique for surface characterization and surfacecleaning.     

Tight—binding calculation of the electronic states of bulk—terminated GaAs（311）A and B surfaces

We have carried out theoretical investigations on the electronic structure of GaAs(311)A and GaAs(311)B surfaces. The bulk electronic structure of GaAs has been described by the second-neighbour tight-binding formalism and the surface electronic structure was evaluated via an analytic Green function method. First, we present the surface band structure together with the projected bulk band of both Ga-terminated and As-terminated for GaAs(311)A and GaAs(311)B surfaces, respectively. In each case, the number of surface states is determined, and the localized surface features and orbital properties of these surface states along Γ-Y-S-X-Γ high symmetry lines of the surface Brillouin zone are discussed. For the Ga-terminated GaAs(311)A (1×1) surface, we have tested two possible structure models, i.e. "the bridge site" and "the hollow site" models. In comparison with the angle-resolved photoelectron spectroscopy studied recently, the results have shown that the surface electronic states of the hollow site model are in good agreement with the experiments, whereas those of the bridge site model are not. So we have concluded that the hollow site model is favourable for the Ga-terminated GaAs(311) (1×1) surface and the bridge site model should be excluded.     

ICP—AES法测定锌及其化合物中的杂质元素

采用样品溶解后直接测定及氢氧化钇共沉淀将锌与被测杂质元素分离后测定相结合，研究了锌及其化合物中Ａｇ，Ｃｏ，Ａｌ，Ｎｉ，Ｆｅ，Ｃｕ，Ｃｄ，Ｃｒ，Ｍｎ，Ｉｎ，Ａｓ，Ｐｂ，Ｓｎ，Ｓｂ，Ｂｉ等１５个杂质元素的ＩＣＰ－ＡＥＳ测定方法，相对标准偏差１．６－８．１％。     

Theoretical Analysis of Characteristics of GaxInl—x NyAsl—y／GaAs Quantum Well Lasers with Different Intermediate Layers

Based on the band anticrossing model, the effects of the strain-compensated layer and the strain-mediated layero n the band structure, gain and differential gain of GalnNAs/GaAs quantum well lasers have been investigated. The results show that the GaNAs barrier has a disadvantage in increasing the density of states in the conduction band. Meanwhile, the multilayer quantum wells need higher transparency carrier density than the GalnNAs/GaAs single quantum well with the same wavelength. However, they help to suppress the degradation of the differential gain. The calculation also shows that from the viewpoint of band structure, the strain-compensated structure and the strain-mediated structure have similar features.     

超导材料Mg1-xAgxB2的比热和电阻率

我们对新型超导化合物MgB2进行了比热和电导性质测量，测量结果显示该材料的超导临界温度为38.9K。另外我们还对Mg1-xAgxB2（x=0,0.1,0.2)的系列样品进行了测量，发现随着Ag含量的增加，样品在超导相变温度附近的比热跳跃明显减小。这可能是由于Ag和g生成合金，而只有少量的Mg才和B化合成MgB2，故其超导成分很少，所以比热跳跃小。但由于Ag原子量比Mg要大得多，所以样品的单位质量比热比纯样品大。当Ag掺杂到0.3时，电阻率测量表明当温度的为4.2K时其电阻仍未到0，超导电性消失。另外我们分别对烧结一次和烧结两次的纯MgB2样品进行了比热测量，测量结果显示烧结过两次的样品的比热比烧结一次的样品的比热要小一些，这说明样品在烧结的过程中可能有部分Mg流失。从而导致其单位质量的比热减少。