Pressure-induced magnetic order in golden SmS

High pressure 149Sm nuclear forward scattering experiments have been performed on the nonmagnetic semiconductor SmS. We present the first clear evidence that the closure of the insulating gap at p(Delta) approximately 2 GPa coincides with the appearance of magnetic order. The pressure-induced magnetic phase transition has some first order character and suggests that the Sm ions are nearly trivalent at p(Delta). A Gamma(8) quartet crystal field ground state with a value of approximately 0.5 micro(B) for the samarium magnetic moment is inferred from our results. Considerable magnetic short range order is observed above the ordering temperature inferred from macroscopic measurements.     

Growth of gold nanoparticle arrays in TiO2 mesoporous matrixes

An interconnected Au nanoparticle arrangement is obtained by electrodeposition from Au(III) soluble complexes within the pore system of block-copolymer templated mesoporous titania films. The resulting Au@TiO2 nanocomposites (5 nm Au particles, 5.5 nm amorphous titania walls) have the electrochemical behavior of a gold electrode of high surface area. The attenuation of Au surface plasmon due to -OH electroadsorption and the existence of mixed localized states in these Au@TiO2 nanocomposites are observed by in situ spectroelectrochemistry.     

Isodifferential derivative approach to the spectrophotometric determination of nickel and cobalt mixtures

A graphical method for measuring derivative amplitudes in binary mixtures with overlapping spectra is described. The method is based on the interference-free character of the isodifferential points in the derivative calibration graphs. Cobalt and nickel mixtures are analyzed in the range 0.01–2.5 μg ml^?1 by the formation of coloured chelates with benzyl-2-pyridylketone 2-pyridylhydrazone, with relative standard deviations ?1.5%.     

Mössbauer study of the NpSb1−xTex solid solutions

²³⁷Np,¹²¹Sb and¹²⁵Te Mössbauer experiments on NpSb_1?xTe_x (0≤x≤0.25) are reported. The data indicate the occurrence of Np³⁺ ions and suggest that the magnetic structure changes from AF-type I to AF-type IA (or ferri++-) by substituting Sb with 5% of Te. The Np ordered moment decreases smoothly with increasing Te content.     

90-fs stretched-pulse ytterbium-doped double-clad fiber laser

We report ultrashort, high-energy pulse generation from a side-pumped Yb-doped double-clad fiber laser. The laser is operating in the stretched-pulse regime. It directly generates 4.8-ps, 5-nJ pulses that are extracavity compressed to 90 fs.     

Observation of extended poloidal structures in the turbulent edge plasma of the L-2M stellarator

Results are reported from an experimental study of the characteristics of the turbulent edge plasma in the L-2M stellarator. Extended coherent structures are observed to form in the poloidal direction. The poloidal coherence length of the fluctuations reaches 20 cm. The coherence of the fluctuations depends appreciably on the poloidal azimuth and is maximum along the outer edge, as is natural for unstable modes in a toroidal plasma. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 9, 634–639 (10 May 1998)     

On the perturbed angular correlation attenuation factor for relaxing systems

The attenuation factor of gamma-gamma perturbed angular correlation in the isotropic random-phase approximation is deduced for an axially symmetric quadrupole interaction and spins 1, 3/2, 2 and 5/2. It is shown that modifications to the usual expression are significant. Useful expressions for fitting procedures are obtained.Work supported in part by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Financiadora de estudos e Projetos (FINEP).