Sign and magnitude of the cobalt hyperfine field in amorphous Co80P20 determined by nuclear orientation

An average cobalt hyperfine field in a Co₈₀P₂₀ amorphous alloy has been determined by measuring the intensity of γ-rays emitted from oriented ⁶⁰Co nuclei. A value of 134 ± 4 kOe is obtained and the sign of the field is negative.     

Structure of 72,74Se at high spin

Lifetimes of high spin states up to { }=22⁺ in the yrast positive parity bands have been measured to investigate the shape evolution with increasing spin in ^{72, 74}Se. The Q _t values derived from these measurements indicate that prolate shape stabilizes for ⁷²Se, while a triaxial shape develops for ⁷⁴Se at higher spins. Comparison of the observed trend in Q _t with spin for ^{72, 74}Se with that of the corresponding kryptones isotones emphasizes the stability provided by N=38 prolate shell gap even at high rotational frequency.     

Noncollinear magnetic hyperfine fields in the Ag spacers of Fe/Ag multilayers

Nearly perpendicular magnetic hyperfine fields have been observed for the first time in the Ag "spacers" of Fe/Ag multilayers using low temperature nuclear orientation of (110)Ag(m) at 6 mK. At the same time, vibrating sample magnetometry measurements at temperatures down to 4 K have shown the magnetic anisotropy of the Fe to be in plane. The direction of the Ag hyperfine field is thus noncollinear (nearly orthogonal) to the Fe anisotropy. These results are compared with full potential linearized augmented plane wave calculations using the wien97 code.     

Impurities in Magnetic Insulators Studied by Low-Temperature Nuclear Orientation

Although the effects of impurities in metallic magnets have been extensively studied there have been far fewer experiments on impurities in insulating magnets, and, in an effort to understand this problem, we have investigated the effect of impurities in various systems. In MnCl₂⋅4H₂O samples doped with 1.6, 4.0 and 6.2% Co, the ⁵⁴Mn NMRON line is significantly broadened compared to the line in the pure crystal and shows structure on the low frequency side. The nuclear spin-lattice relaxation time is also lower by an order of magnitude. ⁵⁴Mn has also been doped into FeCl₂⋅4H₂O for which a 4-sublattice structure has been proposed and some details of this structure have been obtained. This revised version was published online in September 2006 with corrections to the Cover Date.     

Nuclear spin-lattice relaxation in 3d ferromagnetic metals

The contributions to nuclear spin-lattice relaxation at low, intermediate and high applied magnetic fields in 3d ferromagnetic alloys are discussed. The analysis of nuclear orientation experiments is considered and the various experimental techniques briefly reviewed. Some results for the relaxation rate for cobalt nuclei in iron are compared and some recent high-field data for⁶⁰CoFe are presented showing that an indirect spin-wave process is relatively weak.     

Materials doping through sol–gel chemistry: a little something can make a big difference

Several examples of sol–gel preparation of doped materials are taken to illustrate the various situations where the doping elements are responsible for the main function of the material or govern its structure. Other examples are used to illustrate that sometimes unexpected effects can be observed like structural modification and the appearance of new properties. Rare earth doped scintillators demonstrate higher homogeneity for materials prepared via sol–gel chemistry when compared with classical solid state reaction. The XRD study of rare earth doped orthoborates shows that doping can affect the vaterite to calcite phase transition observed in these compounds. A Raman spectroscopic study has been performed on doped silica xerogels and it has been shown that doping ions can modify greatly the densification process in these amorphous materials. Finally, it has been evidenced that sol–gel chemistry allows the preparation of bioactive ceramics with enhanced properties. In particular Zn-doped HAP with anti inflammatory properties has been prepared and Sr-doped bioactive glasses have demonstrated superior in-vitro bioactivity as evidenced by PIXE-RBS study.     

抗坏血酸有机锗倍半氧化物的合成及抗癌活性研究

通过三氯锗仿与抗坏血酸分子的加成反应,合成了一种新型有机锗倍半氧化物,产物的结构通过元素分析、IR及UV光谱等方法进行了表征．生物活性实验表明合成物对小鼠S-180肿瘤生长具有显著的抑制作用．     

Raman Spectroscopic Investigations of the Effects of Ag+ and Ce3 + Doping on the Densification of Nanoporous Silica Xerogels

Doped and undoped 50 Å porous silica xerogels were heat-treated at various annealing temperatures ranging from 800°C to 1150°C. The heating was performed in air for 1 hour at each temperature. Raman spectroscopy was used to follow the structural changes occurring at various stages of the gel-to-glass transformation, as well as to investigate the effects of metal ions on the densification of these nanoporous silica xerogels. Raman data and density measurements showed that while densification is completely achieved at 1050°C for undoped xerogels, it occurs at 950°C for Ag⁺-doped samples. On the other hand, Ce^{3 +} doping was found to slow down the densification process, with complete densification occurring at 1100°C.     

电感耦合等离子体原子发射光谱法测定钛酸钡纳米粉体中7种杂质元素

钛酸钡纳米粉体样品用盐酸溶解,在所得样品溶液中用电感耦合等离子体原子发射光谱法测定了以氧化物存在于样品中的7种杂质元素(包括镁、锶、钾、钠、铝、硅及铁),对测定的光谱条件进行了试验并优化达到上述各元素的测定上限为0.1%(质量分数).测得方法的检出限(3S/b)为(单位μg·L-1):2.0(铝),1.0(铁),20.0(钾),0.2(镁),4.0(钠),3.0(硅)及0.5(锶).应用此方法分析了两件实样,所得结果的相对标准偏差(n=6)小于等于2.0%,对其中4种杂质元素(镁、钾、钠和锶)同时用HG/T 3587-1999标准中的方法作分析校核,所得结果与此方法结果一致.     

Raman spectroscopic investigations of the effect of the doping metal on the structure of binary tellurium-oxide glasses

Raman studies over the range 10 to 1000 cm⁻¹ have been performed on binary tellurium-oxide glasses (1-x)TeO₂-xMO (M = Pb,Zn or Mg) prepared using a conventional melt technique. The intensities and positions of Raman bands observed in the range above 250 cm⁻¹ were found to depend both on the compound oxide and on the amount of doping. Indeed, the ratio of the intensity of the band around 680 cm⁻¹ (assigned to vibrations of TeO₄ trigonal bipyramids) with respect to that of the component around 750 cm⁻¹ (related to stretching-vibrations in TeO₃₊₁, TeO₃ and MO groups) are affected in different ways for the glass-modifier MgO and for the intermediate glass-formers PbO and ZnO. Concurrently, an explicit dependence on the compound oxide and amount of doping was also observed on the maximum of the boson peak (BP) in the low-frequency region around 40 cm⁻¹. The structural correlation lengths in the glasses, calculated using the model described by Shuker and Gammon, were found to be about 0.50 nm (1-x)TeO₂-xMgO glasses and around 0.65 nm for (1-x)TeO₂-xMO (M = Pb or Zn) glasses. All these results are interpreted in terms of the effect of the metal oxide on the changes induced in the structural arrangements of ¹_χ[TeO₄-TeO₃] chains.