[en] [Tb(Fe_0.55Co_0.45)_1.5/Fe]_n and [Tb(Fe_0.55Co_0.45)_1.5/(Fe_0.5Co_0.5)]_n multilayers were fabricated by rf-magnetron sputtering from composite targets. Magnetostriction was measured using an optical deflectometer. The as-deposited films showed a soft magnetic and magnetostrictive character, with a coercive field μ₀H_c=5 mT and a parallel magnetostrictive susceptibility χ_λ#parallel#=dλ_#parallel#/d(μ₀H)=1.4times10^-2 T^-1. This magnetostrictive softness was strongly improved by heat treatments: the magnetostrictive susceptibility attains the huge value of 5times10^-2 T^-1 in applied field of 6 mT. The low-field dependence of the magnetostrictive susceptibility and their technical characters are described in detail. [copyright] 2001 American Institute of Physics

[en] Correlation ratios between the mean square displacement (MSD), mean square relative displacement (MSRD), and correlated displacement function were studied in extended X-ray absorption fine structure spectra (EXAFS). The expressions of MSD, MSRD, and correlation function were determined using Debye models. Hardy problems due to many-particles effects were considered and replaced by a calculation based on the effective anharmonic potential, including the interaction of absorbing and scattering atoms with their nearest neighbours atoms. Based on the Debye-Waller factor, the difference between MSRD and MRD was analyzed, and their ratios have calculated. The methods were applied to fcc crystals and their alloys. Numerical results for Cu, Ag crystals and CuAg50 alloys agreed with experimental values and other studies. (paper)

No abstract available

No abstract available

[en] Ni_0.5Mn_0.5-xSb_x (x = 0.1, 0.2, 0.3, and 0.4) ingots fabricated by arc-melting high-pure metals have been studied to determine their structure and magnetic properties and to identify the magnetocaloric effect. X-ray diffraction analyses reveal that the sample with x = 0.2 is close to a single phase in a cubic structure while the others have the secondary phases. This influences strongly the magnetic properties of Ni_0.5Mn_0.5-xSb_x. With increasing Sb content, the Curie temperature (T_C) increases from ∼ 210 (for x = 0.1) to 435 K (for x = 0.4). Among the studied alloys, two samples, x = 0.2 and 0.3, have the greatest saturation magnetization values, which were recorded at 300 K. Under an applied field of 12.0 k Oe, the maximum magnetic entropy changes are about 1.0 and 0.5 J·kg · K^-1 for x = 0.2 and 0.3, respectively. Detailed analyses related to isothermal M-H curves in the vicinity of T_C by using the modified Aerate method reveal that these samples undergo a second-order phase transition with critical exponents of β = 0.40 ± 0.01 and γ = 1.27 ± 0.08 for x = 0.2 and of β = 0.69 ± 0.09 and γ = 0.85 ± 0.10 for x = 0.3. The differences in the critical parameters are likely related to the presence of Ni-related secondary phases.

[en] A source of polarized electrons based on a helium flowing afterglow has been developed at Orsay. This source, SELPO-M, has been placed on a 100 kV platform and set up in such a way as to allow its connection to the MAMI accelerator. Its performances in terms of current, polarization and optical properties are given. Its figure of merit (IP²≅75 μA) appears highly competitive as compared to strained GaAs sources. (author)

No abstract available

No abstract available

[en] Exchange-spring TbFeCo/YFeCo multilayers exhibit interesting magnetic and magnetostrictive properties that are rather promising for application in microsystems. In this paper, we present a study of the effect of the exchange coupling on the magnetic properties of these magnetostrictive multilayers. An exchange bias phenomenon, revealed by a shift of the minor hysteresis loop along the applied field axis, is found as the result of the creation of interfacial domain walls. This effect strongly depends on the magnetic properties of the soft YFeCo layer, and becomes more pronounced at low temperatures due to the enhancement of the magnitude of the exchange coupling between the layers.

[en] In a search for very rare decays of the K⁺ meson the K⁺→μ⁺γe⁺e^- and K⁺→e⁺γe⁺e^- modes with branching ratios of (10 +- 3) x 10^-7 and (2 +- 2) x 10^-7 respectively were observed. New limits were also put on a decay allowed by the alternate scheme of lepton conservation K⁺→π^-μ⁺e⁺, on a decay with double charged weak current K⁺→π^-e⁺e⁺ and on other forbidden decays K⁺→μ^-γe⁺e⁺ and K⁺→π⁺μ^+-e^-+. (Auth.)