Ferromagnetic resonance and magnetic microstructure in nanocomposite films of Cox(SiO2)1 ? x and (CoFeB)x(SiO2)1 ? x

This paper reports on the results of the investigation of the relation between the magnetic microstructure and ferromagnetic resonance (FMR) in ferromagnetic metal-insulator composites by using granular alloys (Co₄₁Fe₃₉B₂₀) _x (SiO₂)_{1 − x} and Co _x (SiO₂)_{1 − x} as an example. A comparative analysis of the properties of FMR spectra and parameters of random magnetic anisotropy leads to correlations between these quantities. It has been found that the main mechanism that determines the FMR line width in the films under investigation is the exchange narrowing mechanism.     

(La0.7Sr0.3MnO3 )m(BiFeO3)n 超晶格结构的导电机理

利用射频磁控溅射的方法在SrTiO₃(001) 基片上制备了(La_0.7Sr_0.3MnO₃)_m(BiFeO₃)_n超晶格结构.对所制备的超晶格结构进行了50—150℃温度范围内的电流-电压测试分析.结果表明,随着BiFeO₃薄膜的厚度减小,温度的升高,(La_0.7Sr_0.3MnO₃)_m(BiFeO₃)_n超晶格结构的电流变大.进一步根据介质导电模型对(La_0.7Sr_0.3MnO₃)_m(BiFeO₃)_n超晶格结构的导电特性做了分析.在温度较低或者电场较弱时,所制备的(La_0.7Sr_0.3MnO₃)_m(BiFeO₃)_n超晶格结构表现为欧姆导电,而在高温,高电场的情况下,其导电行为由空间电荷限制电流机理主导. 关键词： 超晶格薄膜 多铁 空间电荷限制电流     

Tuning X/(TiO2)x–(SiO2)100 – x (0 < x < 40) xerogel photocatalysts

Microporous (TiO₂) _x –(SiO₂)_{100 − x} (0 < x < 40) xerogels have been produced by sol–gel methods either by partial pre-hydrolysis or reflux of tetraethoxysilane and titanium isopropoxide. These have been characterised by ²⁹Si nuclear magnetic resonance, X-ray diffraction, EXAFS at the Ti–K edge, X-ray photoelectron spectroscopy, temperature-programmed reduction, FT infrared, N₂ adsorption at 78 K (BET), transmission electron microscopy and dynamic light scattering (DLS). These were dip coated onto fused silica and characterised by atomic force microscopy and UV–visible absorption. Their photoactivity in removal of alkylphenol ethoxylate TX100 from water was less than for less porous titania. The advantages of including thermally removable PEG or PPG templates in terms of increasing surface, meso-porosity and photon absorbance at visible wavelengths to give nanoengineered photocatalytic films are described.     

Au10(TBBT)10:Aun(TBBT)m纳米团簇的起点与终点

Gold(I) thiolate compounds (i.e. Au^I-SR) are important precursors for the synthesis of atomically precise Au_n(SR)_m nanoclusters. However, the nature of the Au^I-SR precursor remains elusive. Here, we report that the Au₁₀(TBBT)₁₀ complex is a universal precursor for the synthesis of Au_n(TBBT)_m nanoclusters (where TBBT=4-tertbutylbenzenethiol/thiolate). Interestingly, the Au₁₀(TBBT)₁₀ complex is also found to be re-generated through extended etching of the Au_n(SR)_m nanoclusters with excess of TBBT thiol and O₂. The formation of well-defined Au₁₀(TBBT)₁₀ complex, instead of polymeric Au^I-SR, is attributed to the bulkiness of the TBBT thiol. Through 1D and 2D NMR characterization, the structure of Au₁₀(TBBT)₁₀ is correlated with the previously reported X-ray structure, which contains two inter-penetrated Au₅(TBBT)₅ rings. The photophysical property of Au₁₀(TBBT)₁₀ complex is further probed by femtosecond transient absorption spectroscopy. The accessibility of the precise Au₁₀(TBBT)₁₀ precursor improves the efficiency of the synthesis of the Au_n(TBBT)_m nanoclusters and is expected to further facilitate excellent control and understanding of the reaction mechanisms of nanocluster synthesis.     

Optical properties of (In2Se3)1–x·(CuIn5Se8)x solid solutions

Single crystals of In₂Se₃ and CuIn₅Se₈ compounds and (In₂Se₃)_1–x·(CuIn₅Se₈)_x solid solutions have been grown from the melt using the Bridgman method and their composition and structure determined. It is shown that the crystals have n-type conductivity. Their transmission spectra were studied in the self-absorption edge region at 80 and 295 K. Based on the spectral measurements, the band gap width (E_g) was determined and the band gap concentration dependences were plotted. It is found that E_g varies with the x composition nonlinearly. Using the dielectric model of Van Vechten–Bergstresser and the Hill–Richardson pseudo potential model, E_g(x) was calculated theoretically.     

Elektronen-Spin-Resonanz an (La1??xGdyCex)Al2

In the EPR of (La_1––x Gd _y Ce _x )Al₂ a bottleneck in the relaxation of the conduction electrons to the lattice is present at sufficiently high Gd-concentrations. The bottleneck can be broken by decreasing the Gd-concentration or by adding Cerium as a spin-flip-scatterer.g-factor and line broadening are measured for (La_1–y Gd _y )Al₂ and (La_1––x Gd _y Ce _x )Al₂ as a function of temperature and Gd- and Ce-concentrations. The Cerium induced relaxationsrate _eL (Ce) increases linearly with Ce-concentration up tox0.025. This corresponds to the fact, well known by measurements of the Kondo anomalies, that Cerium impurities show no significant interaction up to rather high concentrations.     

(Bi1-x Agx)2(Te1-ySey)3粉体的机械合金化制备及其放电等离子烧结体的热电输运特性

采用机械合金化制备了n型(Bi_1-xAg_x)₂(Te_1-ySe_y)₃合金粉体,对其进行XRD分析表明Bi,Te,Ag,Se单质粉末,经2h球磨后实现了合金化;SEM分析表明随着机械合金化时间延长粉体颗粒变得均匀、细小,颗粒尺寸在微米至亚微米数量级.采用放电等离子烧结制备了块体样品,研究了合金成分和球磨时间对热电性能的影响.结果表明材料的热电性能与掺杂元素有密切关系,Ag有利于提高功率因子和降低晶格热导率,球磨10h的(Bi_0.99Ag_0.01)₂(Te_0.96Se_0.04)₃合金粉末的烧结块体具有最大的功率因子和最低的晶格热导率,并在323K取得最高ZT值0.52. 关键词： 1-xAg_x)₂(Te_1-ySe_y)₃合金')" href="#">(Bi_1-xAg_x)₂(Te_1-ySe_y)₃合金 机械合金化 放电等离子烧结 热电性能     

Structural and electrical investigation of (Ag3AsS3)x(As2S3)1?x superionic glasses

Structural studies of (Ag₃AsS₃) _x (As₂S₃)_1−x chalcogenide superionic glasses in the compositional range x = 0.3–0.9 were performed by scanning electron microscopy. Temperature and compositional dependences of transmission coefficient, electrical conductivity, and activation energy were investigated     

(Fe1-xCox)3BO5纳米棒磁性的研究

本文采用高温有机溶剂法制备了(Fe_1-xCo_x)₃BO₅纳米棒, 通过控制反应物中乙酰丙酮钴的含量合成了不同Co含量的(Fe_1-xCo_x)₃BO₅. 利用高分辨透射电子显微镜(HRTEM)、超导量子干涉磁强计(SQUID)对其形貌和磁性能进行了表征. 高分辨透射电子显微镜结果表明制备出的纳米(Fe_1-xCo_x)₃BO₅为多晶棒状, 且具有多折孪晶结构; 磁性测量的结果表明,(Fe_1-xCo_x)₃BO₅纳米棒在室温下表现出铁磁性, 随着Co含量的增加, 纳米棒的铁磁性逐渐增加, 该纳米棒有望用来研究生物大分子的机械性能.     

Magnetic phase transitions in Nd1 ? xDyxFe3(BO3)4 ferroborates

The magnetic properties of ferroborate single crystals with substituted compositions Nd_{1 − x} Dy _x Fe₃(BO₃)₄ (x = 0.15, 0.25) with competing exchange Nd-Fe and Dy-Fe interactions are investigated. For each composition, we observed a spontaneous spin-reorientation transition from the easy-axis to the easy-plane state and step anomalies on the magnetization curves for the spin-flop transition induced by a magnetic field B | c. The measured parameters and effects are interpreted using a unified theoretical approach based on the molecular field approximation and on calculations performed in the crystal-field model for the rare-earth ion. The experimental temperature dependences of the initial magnetic susceptibility from T = 2 K to T = 300 K, anomalies on the magnetization curves for B | c in fields up to 1.8 T, and their evolution with temperature, as well as temperature and field dependences of magnetization in fields up to 9 T are described. In the interpretation of experimental data, the crystal-field parameters in trigonal symmetry for the rare-earth subsystem are determined, as well as the parameters of Nd-Fe and Dy-Fe exchange interactions.     

Magnetic and ferroelectric properties of exchange-frustrated multiferroics (Ni1 ? xTx)3V2O8 (T = Co, Mn, Zn)

The effect of the substitution of Co²⁺, Mn²⁺, and Zn²⁺ ions for Ni²⁺ ions on the magnetic, dielectric, and ferroelectric properties of vanadate single crystals (Ni_{1 − x} T _x )₃V₂O₈ has been analyzed. It has been found that the low-level (x ≤ 0.1) substitution of both magnetic and nonmagnetic ions stabilizes the ferroelectric state with a cycloidal magnetic structure. The existence region of this state is expanded to low temperatures down to 3 K for Zn²⁺ and below 1.8 K for Co²⁺ and Mn²⁺ owing to the suppression of a low-temperature weak ferromagnetic phase. At the same time, the ferroelectric phase disappears completely at large concentrations of Co and Mn. The effect of magnetic fields on the magnetic and ferroelectric states has been analyzed. It has been shown that the magnetic field along the c axis suppresses the ferroelectric state, whereas the magnetization along the antiferromagnetism axis (a axis) induces the reentrant phase transition from a paraelectric weak ferromagnetic structure to a ferroelectric structure. The corresponding H-T phase diagrams have been drawn.     

XANES and USXES studies of interatomic interactions in (Co41Fe39B20)x(SiO2)1 ? x nanocomposites

The electronic structure and phase composition of (Co₄₁Fe₃₉B₂₀) _x (SiO₂)_{1 − x} nanocomposites are studied by x-ray absorption near-edge spectroscopy, which is extremely sensitive to the chemical environment of elements in multicomponent compounds. An analysis of the recorded Fe L _{2, 3}, Co L _{2, 3}, B K, Si L _{2, 3}, and O K absorption spectra demonstrates interatomic interactions between the elements of the metallic and dielectric components of the nanocomposites. As a result of these interatomic interactions, a complex multiphase system, whose electronic structure should determine the transport and magnetic properties of the nanocomposites, forms. In particular, the transformation of the fine structure of the iron L _{2, 3} spectra reflects a change in the ratio of divalent to trivalent iron in its oxides and/or silicates. CoO and complex boron oxides are found to exist in the nanocomposites. The electrical conductivity of a FeO · F₂O₃ · CoO grain embedded in the silicate-oxide medium of the nanocomposites is controlled by electron exchange between Co²⁺, Fe²⁺, and Fe³⁺ ions. The dielectric component consists of a mixture of silicon oxide and the silicates/borosilicates of transition metals. Original Russian Text ? é.P. Domashevskaya, S.A. Storozhilov, S.Yu. Turishchev, V.M. Kashkarov, V.A. Terekhov, O.V. Stogneĭ, Yu.E. Kalinin, A.V. Sitnikov, S.L. Molodtsov, 2008, published in Fizika Tverdogo Tela, 2008, Vol. 50, No. 1, pp. 135–141.     

(La0.7Sr0.3MnO3)m(BiFeO3)n超晶格间隔的La0.7Sr0.3MnO3三明治结构制备及表征

采用射频磁控溅射的方法在SrTiO₃（001） 基片上制备了（La_0.7Sr_0.3MnO₃）_m（BiFeO₃）_n超晶格间隔的La_0.7Sr_0.3MnO₃三明治结构.X射线衍射分析证明（La_0.7Sr_0.3MnO_{关键词： 超晶格薄膜 电诱导效应 隧道效应}     

Electrical and magnetic properties of [(CoFeZr)x(Al2O3)1 ? x/(α-SiH)]n multilayer structures

The concentration dependences of the electrical resistivity and complex permeability of [“(Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} ”/“α-Si: H”] _n multilayer structures and (Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} composites have been studied. It has been established that introduction of a semiconductor interlayer into the (Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} composites substantially decreases the electrical resistivity of [“(Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} ”/“α-Si: H”] _n multilayer structures. The concentration dependences of the real and imaginary parts of the complex permeability of the [“(Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} ”/“α-Si: H”] _n nanomultilayer structures substantially differ from those of the (Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} composites. The real part of the complex permeability of the [“(Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} ”/“α-Si: H”] _n nanomultilayer structures follows the curve with a minimum near the percolation threshold of the composite, and the imaginary part smoothly decreases as the ferromagnetic phase concentration increases. The results obtained are explained by the increase in the bifurcation temperature due to the conduction electrons of the semiconductor interlayer, which favor magnetic ordering of ferromagnetic grains.     

Co(S1-xSex)2系统中的铁磁量子相变

针对Co(S_1-xSe_x)₂系统在x=0.11附近发生的铁磁金属到顺磁金属相变,制备了一系列不同Se替代浓度的多晶样品.通过对其结构和电阻率-温度ρ(T)关系的系统观测,结果发现,样品铁磁相变温度T_C随着Se替代浓度x值的增加,以(1-x)^1/2关系单调下降,其二级铁磁相变转变为一级相变 关键词： 量子相变 自旋量子涨落 1-xSe_x)₂')" href="#">Co(S_1-xSe_x)₂     

Profile of the refractive index distribution over the depth of (HfO2)x(Al2O3)1 ? x films

Capabilities of the method of laser null ellipsometry for the study of optical parameters of thin films of multicomponent alloys are demonstrated. Films of alloys (HfO₂) _x (Al₂O₃)_{1 − x} on single-crystal silicon are obtained by the chemical vapor deposition with the use of the following volatile compounds: hafnium dipivaloylmethanate (IV) and aluminum acetylacetonate (III). The selection of initial sets for their optical parameters is justified. The selected model is shown to correspond to experimental data. In films deposited from the mixture of precursors, the refractive index increases from a substrate to a film surface. Due to the separation of sources, films described by a single-layer model were deposited. This fact is indicative of the homogeneous distribution of components over the film thickness.     

GeO2-Bi2O3-MOx(MOx=WO3, BaO)玻璃近红外超宽带发光的研究

用高温熔融法制备了(99.5-χ) GeO₂-χBaO-0.5Bi₂O₃(χ=3, 6, 9mol%)与(99.5-φ)GeO₂-φWO₃-0.5Bi₂O₃(φ=3，6，9mol%)玻璃，测定了样品的发射光谱(800nmLD激发)、吸收光谱、荧光衰减和差热曲线.实验结果表明，在GeO₂-WO₃-Bi₂O₃系统玻璃中，随着WO₃含量的增加，在1260nm处的发光强度增强，荧光半高宽(FWHM)增宽，荧光寿命增长，而且玻璃的吸收边带发生明显的红移；在GeO₂-BaO-Bi₂O₃系统玻璃中，随着BaO含量的增加，玻璃在1290nm处发光强度增强，FWHM增宽，荧光寿命增长，吸收边带也有明显的红移.从吸收边带发生红移的情况，结合发射光谱和荧光衰减曲线特性，我们推断玻璃样品在近红外的宽带发光可能由Bi⁵⁺离子所引起.从荧光特性估算了玻璃的σ_p×τ和σ_p×Δλ值，这些玻璃均具有较小的σ_p×τ和较大的σ_p×Δλ特性，说明GeO₂-Bi₂O₃-MO_x(MO_x=WO₃, BaO) 系统玻璃是研制成近红外(O到S波段)超宽带光纤放大器的良好材料.     

Pr0.7(Sr1-xCax)0.3MnO3多晶体系中的小极化子性质

采用基于柠檬酸体系的溶胶-凝胶法制备了Pr_0.7（Sr_1-xCa_x）_0.3MnO₃系列的多晶块材, 同时还用脉冲激光沉积技术（PLD）在SrTiO₃（100）衬底上外延生长了同一系列的薄膜, 系统研究了它们的晶格结构和电输运行为. 多晶和薄膜样品都具有正交晶格结构, 电输运行为在居里温度T_Ｃ以上的高温顺磁相都很好 关键词： 0.7（Sr_1-xCa_x）_0.3MnO₃')" href="#">Pr_0.7（Sr_1-xCa_x）_0.3MnO₃ 绝热小极化子模型 双交换作用 Jahn-Teller晶格畸变     

Magnetic anisotropy and magnetoelectric properties of Tb1 ? xErxFe3(BO3)4 ferroborates

Magnetic and magnetoelectric properties of ferroborate single crystals with complex composition (Tb_{1 − x} Er _x Fe₃(BO₃)₄, x = 0, 0.75) and with competing exchange Tb-Fe and Er-Fe interactions are investigated. Jumps in electric polarization, magnetostriction, and magnetization are observed as a result of spin-flop transitions, as well as a considerable decrease in the critical field upon an increase in the Er concentration, in a field H _c parallel to the c axis. The observed behavior of phase-transition fields is analyzed and explained using a simple model taking into account anisotropy in g factors and exchange splitting of funda-mental doublets of the easy-axis Tb³⁺ ion and easy-plane Er³⁺ ion. It is established that magnetoelectric and magnetostriction anomalies under spin-flop transitions are mainly controlled by the Tb subsystem. The Tb subsystem makes a nonmonotonic contribution ΔP _a (H _a , T) to polarization along the a axis: the value of ΔP _a reverses its sign and increases with temperature due to the contribution from the excited states of the Tb³⁺ ion. Original Russian Text ? A.K. Zvezdin, A.M. Kadomtseva, Yu.F. Popov, G.P. Vorob’ev, A.P. Pyatakov, V.Yu. Ivanov, A.M. Kuz’menko, A.A. Mukhin, L.N. Bezmaternykh, I.A. Gudim, 2009, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2009, Vol. 136, No. 1, pp. 80–86.