Structure and Physical Properties and Charge Ordering in La2-xSrxMnO4 （1.125 ≤x≤2.0）

Structural measurements have revealed nonlinear changes of lattice parameters in the layered-perovskite manganires La2-xSrxMnO4 with increasing Sr content; these changes can be well understood by means of interactions among the charge, crystal lattice and the orbital degree of freedom in this strongly correlated system. A probably spin-glass transition was detected for the first time in the x=1.75 sample at the temperature of around 44K. Fundamental properties of charge ordering appearing in the range of 1.5 ≤x≤1.75 have been observed at low-temperatures and are interpreted in terms of the Mn^3 -dz^2 orbital ordering.     

Preparation and the physical properties of antiperovskite-type compounds Cd1_xInxNNi3（n〈x〈0.2）and Cd1-yCuyNNi3（0〈y〈0.2）

Two series of Cdl-xInxNNi3 （0 〈 x 〈 0.2） and Cd1_yCuyNNi3 （0 〈 y 〈 0.2） samples were prepared from CdO, In203, CuO, and nickel powders under NH3 atmosphere at 773 K. The structural and physical properties were investigated by means of X-ray powder diffraction temperature-dependent resistivity and magnetic measurements. X-ray powder diffraction results showed that the Cd1-xInxNNi3 and Cd1_yCuyNNi3 compounds have a typical antiperovskite structure, and the CdNNi3, Cd0.9In0.1NNi3, and Cd0.9Cu0.1NNia compounds show metallic temperature-dependent resistivity and exhibit a Fermi liquid behavior at low temperature. In contrast to the paramagnetism previously reported, the CdNNi3 sample exhibits very soft and weak ferromagnetism, and no superconductivity was found in the Cd1-xInxNNi3 and Cdl-yCuyNNi3 samples down to 2 K. Each sample exhibited very soft and weak ferromagnetism, and the temperature dependence of the magnetization of the Cd1-xInxNNi3 and Cd1_yCuyNNi3 samples can be well fitted to the combination of a Bloch term and a Curie-Weiss term.     

Nd0．3Sro．7Mn1-xCrxO3（0．01≤x≤0．15）的低温热导率研究

报道Nd0．3Sro．7Mn1-xCrxO3（0．01≤x≤0．15）的热导率在10-300K温区内随温度和Cr含量的变化关系,在所测温区，随着Cr掺杂的增加，样品热导率值整体上逐渐减小，但在x=0．15时，出现反弹．热导率值在绝缘体-金属转变附近有很大提高，这个提高随Cr含量的增加逐渐被压制，直到x=0．15消失．分析指出热导率在绝缘体-金属转变附近的提高是由声子热导率和自旋相关热导率两部分贡献的；Cr掺杂通过电荷、晶格和自旋相互作用影响和制约了热导率随温度的变化,结果表明体系中自旋对热导率的调制作用是不可忽略的。     

Magnetic properties and magnetostriction of PrxNd1-xFe1.9（0≤x≤1.0） alloys at low temperature

The crystal structure,magnetic and magnetostrictive properties of high-pressure synthesized Prx Nd1-xFe1.9(0≤x≤1.0) alloys were studied.The alloys exhibit single cubic Laves phase with MgCu 2-type structure.The initial magnetization curve reveals that Pr0.2Nd0.8Fe1.9 has a minimum magnetocrystalline anisotropy at 5 K.The magnetostriction curve at 5 K shows that Pr0.2Nd0.8Fe1.9 has a very good low-field magnetostrictive property,and the magnetostriction of the PrxNd1-xFe1.9 alloy in high magnetic field is attributable mainly to Pr.The temperature dependence of the magnetostriction(λ ||) at the field of 5 kOe shows that the substitution of Nd reduces the K 1 remarkably,and the values of λ|| of Pr0.2Nd0.8Fe1.9 and Pr0.8Nd0.2Fe1.9 alloys are nearly five times larger than that of the PrFe 1.9 alloy below 50 K;the λ|| of Pr0.8Nd0.2Fe1.9 reaches up to 1082 ppm at 100 K,which makes it a potential candidate for application in this temperature range.     

Multiferroic properties and exchange bias in Bi1-xSrxFeO3 （x = 0-0.6） ceramics

Multiferroic properties and exchange bias(EB) in Bi1-xSrxFeO3(x = 0–0.6) ceramics synthesized by a modified Pechini method are investigated. Sr concentration dependence of structure distorting, ferroelectric properties, and dielectric properties were studied at room temperature. Appropriate Sr doping(x = 0.05–0.2) has been found to decrease the conductivity, enhance ferroelectric properties and give rise to high dielectric constant. Compared with antiferromagnetic BiFeO3 compound, BSFO-x(0 ≤ x ≤ 0.4) ceramics show weak ferromagnetism at room temperature, and their exchange bias field and vertical magnetization shift are observed and exhibit a strong dependence on the content of Sr. This observed EB effect which keeps stable in BSFO ceramics at 10 K tend to vanish at room temperature with Sr concentration over 0.4.     

立方C15b型YbCu_(5-x)In_x(0≤x≤1)中的原子混合价态与价态转移

利用电弧熔炼方法制备了YbCu5-xInx(x=0.2,0.4,0.6,0.8,1)稀土金属相间化合物样品.多晶X射线衍射分析表明样品具有立方C15b型结构,并发现其晶胞参数随In含量的增加而线性增加.利用SQUID技术测量了样品在4.2K和300K之间的磁化强度与温度变化曲线,结果表明YbCu4In在40K附近显示出明显的具有一级相变特征的Yb离子价态转移现象;在150K以上YbCu5-xInx样品显示居里-外斯型(Curie-Weiss)型顺磁行为,Yb离子为局域三价态(Yb3+,4f13,J=7/2,μeff=4.54μB),这和先前报道的文献一致.     

Growht and defects in YbxY1—xAl3（BO3）4 crystals

YbxY1-xAl3(BO3)4(x=0.1,0.07 and 0)crystals have been grown by the flux method.The growth defects of YbxY1-xAl3(BO3)4 crystals were detected by X-ray topography.It is found that the perfcetion of YbYAB crystal with low Yb dopant is better than that with high Yb dopant.In Yb0.1Y0.9Al3(BO3)4 crystal,growht bands,growth boundaries,grown-in dislocations and inclusions were observed.Howver,the densities of growth defects for Yb0.07Y0.93Al3(BO3)4 and YAl3(BO3)4 are low and no obvious inclusions are observed in these crytals.In addition,growth twins wrer detected in YbxY1-xAl3(BO3)4 crystal by using the chemical etching method.It is found that the growth twins occur frequently in Yb0.01Y0.9Al3(BO3)4 crystal whereas no growth twin appears in YAl3(BO3)4 crystal. Based on the experimental observations,the formation mechanism of growth twins is discussed.In the meantime,the effective measures for reducing the growth twins and defects are proposed.2001 Elsevier Science B.V.All rights reserved.     

La0.4Ca0.6Mn1-xCrxO3（x=0.00,0.08）的磁电性质研究

用固相反应法制备了La0.4Ca0.6Mn1-xCrxO3（x=0.00,0.08）多晶样品,通过XRD谱、M-T曲线、ρ~T曲线、Lnρ-T-14曲线,研究Cr^3＋替代Mn3＋对La0.4Ca0.6MnO3电荷有序相及电输运性质的影响.实验结果表明：Cr^3＋替代Mn3＋对La0.4Ca0.6MnO3电荷有序相影响...     

Growth,defects,and properties of GdCa4O（BO3）3 and Nd：GdCa4O（BO3）3 crystals

Pure and neodymium-doped gadolinium calcium oxoborate crystals of high quality were grown by the Czochralski method.The orientation of crystal was precisely determined,and the samples for measurements were prepared.Through synchrotron x-ray topography and high-resolution x-ray diffractometry,the twin structure was discovered.Some properties such as the figure of merit value,and dielectric,piezoelectric,and elastic constants were meausured along with a discussion of the anisotropy of the laser properties.     

Floating zone growth and magnetic and specific heat properties of La0.67Ca0.33Mn1-xFexO3（x=0.00,0.04）single crystals

Single crystals of La_0.67Ca_0.33MnO₃ and La_0.67Ca_0.33Mn_0.96Fe_0.04O₃ were obtained by floating zone method. Laue diffraction pattern and rocking curve of the single crystals show that their quality is good. The magnetic behaviours of these compounds have been studied. Fe doping significantly depresses the magnetic contribution to the total specific heat C_P, but slightly influences the lattice contribution at temperatures above 50K. The peak of C_P shifts towards high temperatures with increasing magnetic field. Both single crystals exhibit the first-order magnetic transition around the Curie temperature.     

Electric and magnetic behaviour in double doped La2/3＋4x/3Sr1/3-4x/3Mn1-xMgxO3

The double-doped La2/3＋4x/3Sr1/3-4x/3Mn1-xMgxO3 samples with fixed Mn^3＋/Mn^4＋ ratio equal to 2/1 are investigated by means of magnetism and transport measurements. Phase separation is observed at temperature higher than T^onset c for x = 0.10 and 0.15. For x = 0.10, rather strong phase separation induces drastic magnetic random potential and results in the localization of carriers. Thus, the varlable-range hopping process dominates. For other samples, there is no or only weak phase separation above T^onset c. Thus, thermal activation mechanism is responsible for the high temperature transport behaviour. For x = 0.20 and 0.25, unexpected AFM behaviour is observed at low temperature. All these results are well understood by considering the special role of the ＂double-doping＂.     

Sr3P2-xVxO8:Eu（0≤x≤2.0）的制备及其发光性能

研究了B位掺杂的Sr3P2-xVxO8(0≤x≤2.0)基质和Eu3+掺杂Sr3-3yEu2yP1.2V0.8O8(0相似文献   

Structural,electronic, and magnetic properties of boron cluster anions doped with aluminum：BnAl-（2〈n〈9）

The geometrical structures, relative stabilities, electronic and magnetic properties of small BnAl-（2〈n〈9）clusters are systematicalyy investigated by using the first-principles density functional theory. The results show that the A1 atom prefers to reside either on the outer-side or above the surface, but not in the centre of the clusters in all of the most stable BnAl-（2〈n〈9） isomers and the one excess electron is strong enough to modify the geometries of some specific sizes of the neutral clusters. All the results of the analysis for the fragmentation energies, the second-order difference of energies, and the highest occupied-lowest unoccupied molecular orbital energy gaps show that B4A1- and B8A1- clusters each have a higher relative stability. Especially, the BsA1-cluster has the most enhanced chemical stability. Furthermore, both the local magnetic moments and the total magnetic moments display a pronounced oddeven oscillation with the number of boron atoms, and the magnetic effects arise mainly from the boron atoms except for the B7A1- and BgA1- clusters.     

The doping effects of BiFe1-xCoxO3 （x=0.0-0.8） in layered perovskite BiaTi3O12 ceramics

BisFe1-xCoxTi3O15 （x=0.0, 0.2, 0.4, 0.5, 0.6, and 0.8） multiferroic ceramics are synthesized in two steps using the solid state reaction technique. X-ray diffraction patterns show that the samples have four-layer Aurivillius phases. At room temperature （RT）, the samples each present a remarkable coexistence of ferromagnetism （FM） and ferroelectricity （FE）. The remnant polarization （2Pr） reaches its greatest value of 14 gC/cm2 at x = 0.6. Remnant magnetization （2Mr） first increases and then decreases, and the greatest 2Mr is 7.8 menu/g when x = 0.5. The magnetic properties for x = 0.4 are similar to those for x = 0.6, indicating that the magnetic properties originate mainly from the coupling between Fe3＋ and Co3＋ ions, rather than from their own magnetic moments.     

Structures of（ΩΩ）0＋and（[1]Ω）1＋in Extended Chiral SU（3） Quark Model

The structures of (ΩΩ)0 and ([1]Ω)1 are studied in the extended chiral SU(3) quark model in which vector meson exchanges are included. The effect from the vector meson fields is very similar to that from the one-gluon exchange (OGE) interaction. Both in the chiral SU(3) quark model and in the extended chiral SU(3) quark model,di-omega (ΩΩ)0 is always deeply bound, with over one hundred MeV binding energy, and ([1]Ω)1 ‘s binding energy is around 20 MeV. An analysis shows that the quark exchange effect plays a very important role for making di-omega (ΩΩ)0 deeply bound.     

第一性原理研究Ni3Al1-xVx（x=0-0.4）的力学和热力学性质

采用第一性原理方法研究了Ni3Al1-xVx(x=0-0.4)的力学性质,发现当V含量为0.1时,Ni3Al1-xVx的块体模量、剪切模量、杨氏模量和硬度都出现极大值,因此V掺杂对于Ni3Al力学性能的提升具有重要作用.另外,还研究了不同压强下Ni3Al0.9V0.1的吉布斯自由能、焓、熵、热容等热力学性质随温度的变化关系,结果表明:在高温高压条件下,Ni3Al0.9V0.1的吉布斯自由能、焓、熵、定压热容都出现明显变化.通过计算Ni3Al0.9V0.1的体膨胀系数,发现压强对于Ni3Al0.9V0.1的体膨胀效应具有明显的抑制作用.     

Moessbauer Studies on Spin Transition in Zinc Dilution Complexes [Fe1—xZnx（dpp）2（NCS）2]py（x=0.05—0.40）

A series of spin transition complexes [Fe1-xZnx(dpp)2(NCS)2]ph(x=0.05,0.10,0.15,0.20,0.25,and 0.40;py=pyridine) has been synthesized and studied by Moessbauer spectroscopy.The high-spin structure is frozen at room temperature,and the induced meta-stable high-spin phase by the so-called rapid cooling method is monitored by temperature and time-dependent Moessbauer spectra.The investigation on dynamic relaxation of the high-spin state to the low-spin state at 80-K reveals sigmoid behaviour and existence of cooperative effect for low diluted complexes.This cooperative effect is wrecked by the dilution of Zn(Ⅱ）ions in Fe（Ⅱ）ion sites,and relaxation curves gradually become to obey the first-order kinetics as the ratio of the dilution increases.     

Charge transport in monolayer poly（3-hexylthiophene） thin-film transistors

It is found that ultrathin poly（3-hexylthiophene） （P3HT） film with a 2.5 nm-thick layer exhibits a higher mobility of 5.0× 10-2 cm2/V-s than its bulk counterpart. The crystalline structure of the as-fabricated ultrathin P3HT layer is verified by atomic force microscopy as well as grazing incidence X-ray diffraction. Transient measurements of the as-fabricated transistors reveal the influence of the interface traps on charge transport. These results are explained by the trap energy level distribution at the interface manipulated by layers of polymer film.     

Effect of Te doping on superconductivity and charge-density wave in dichalcogenides 2H-NbSe2-xTex （x = 0, 0.1, 0.2）

Single crystals of Te-doped dichalcogenides 2H-NbSe2-xTex （x ---- 0, 0.10, 0.20） were grown by vapour transport method. The effect of Te doping on the superconducting and charge-density wave （CDW） transitions has been investigated. The sharp decrease of residual resistance ratio, RRR = R（3OOK）/R（SK）, with increasing Te content was observed, indicating that the disorder in the conducting plane is induced by Te doping. Meanwhile the superconducting transition temperature, Tc, decreases monotonically with Te content. However, the CDW transition temperature, TCDW, shown by a small jump in the temperature dependence of the resistivity near 30 K, increases slightly. The results show that the suppression of superconductivity might be caused by the enhancement of CDW ordering. The disorder has little influence on the CDW ordering.