Results 1 - 10 of 1773
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[en] We have demonstrated the coexistence of superconductivity and ferromagnetism in Bi_3Ni nanostructures which have been prepared by making use of novel chemical-reaction paths. Here, we present recent experiments on novel nanostructures, such as supercrystals consisting of packed Bi_3Ni nanofibers. We have investigated their magnetic and electrical-transport properties by means of XMCD, SQUID magnetometry, pulsed-field susceptometry, and ac-resistance measurements in a wide field and temperature range. Resistivity measurements demonstrate that superconductivity persists well above the Pauli limiting field - with strong anisotropy. These results will be presented in the context of a coexistence of superconductivity and ferromagnetism. Part of this work was performed at the NHMFL and ESRF beamline ID08.
[en] We performed neutron powder diffraction measurements on (Bi0.5Na0.5+x)TiO3 and (Bi0.5+y Na0.5)TiO3 to study the structural evolution induced by the non-stoichiometry. Despite the nonstoichiometry, the local structure (r ≤ 3.5 Å) from the pair distribution function analysis is barely affected by a sodium deficit of up to −5 mol%. With increasing pair distance, however, the atomic pair correlations weaken due to the disorder caused by the sodium deficiency. Although the sodium and the bismuth share the same crystallographic site, their non-stoichiometries have rather opposite effects as revealed from distinctive distortions of the Bragg peaks. In addition, a Rietveld refinement demonstrates that the octahedral tilting is continually suppressed for sodium deficits up to −5 mol%. This is contrary to the effect of the bismuth deficiency, which induces little variation in the octahedral tilting.
[en] Magnetic susceptibility measurements on eight samples of tin-rich and three samples of bismuth-rich Bi-Sn alloys were made from 85K to 300K by Faraday's method. The susceptibilities of the eight tin-rich samples are positive and greater than the susceptibility of pure tin. The values are approximately constant at low temperatures but decreasing a little bit with increasing temperature. This result is interpreted as due to the predominant contribution of the Pauli spin paramagnetic susceptibility. A small decrease in susceptibility with temperature is interpreted as due to the effect of the second order term in the expression for spin paramagnetic susceptibility. The fluctuation of the susceptibility for alloys of different composition is interpreted as due to the effect of the density of states at the Fermi levels. The three samples of bismuth-rich alloys show a transition to diamagnetic property, where the diamagnetism is increased with temperature. This result is predominant and due to the diamagnetic contribution from the ions. The increase in susceptibility with temperature is interpreted as due to an increase in the effective radii of the ions due to thermal expansion. (author)
[en] While bismuth-related states are known to localize carriers in GaAs1-xBix alloys, the localization behavior of distinct Bi pair, triplet and cluster states bound above the valence band is less well understood. We probe localization at three different Bi complex states in dilute GaAs1-xBix alloys using magneto-photoluminescence and time-resolved photoluminescence spectroscopy. The mass of electrons Coulomb-bound to holes trapped at Bi pair states is found to increase relative to the average electron mass in the alloy. This increase is attributed to enhanced local compressive strain in the immediate vicinity of the pairs. The dependence of energy transfer between these states on composition is also explored.
[en] Lead apron is harmful to the human body because it is made at heavy metals, and when worn for long periods of time, it causes pain. Therefore, this paper intended to improve the defects of lead apron by using new material shields. For the comparative evaluation of lead and new material shieldes, the shielding rate and weight were measured and tested based on lead 0.5 mmPb. The rate of shielding was 97% based on lead at 0.5 thickness, while The new material shield T3 showed similar shielding rates as lead in 8 layers, and in T2 these values were measured in 11 layers. In addition, similar shielding rate was measured in 12 layers at B2, and 8 layers in BF, and 4 layers in BF2. Comparing the weight of cases when commercialized with apron, T3, T2 and B2 were heavier than lead apron. But BF, BF2 were lighter than the lead apron. Based on the results of the experiment, T3 and T2 can be used as an alternative to lead if human or environmental hazards are considered a priority. However, BF and BF2 should be used if the reduction of external exposure is considered a priority
[en] For the first time strontium activity in liquid alloys with bismuth has been determined. Values of strontium activity coefficients point out to abrupt negative deviation from ideal behaviour of liquid strontium alloys with bismuth which testifies to a strong interparticle interaction in liquid state and agrees with state diagram of this system
[en] Phase diagrams of Bi-BiTeI, Bi2Te3-Bi0.7I0.3 and Bi0.6Te0.4-Bi0.8I0.2 cross sections of Bi-Bi2Te3-BiI3 ternary system are plotted. Solubility limits for components in the ternary system from the side of Bi-I are established. It is shown that stratification propagates along the cross section of Bi2Te3-Bi0.7I0.3 up to 8 at.% Te, Bi0.6Te0.4-Bi0.8I0.2 - up to 5 at.% Te and Bi0.8Te0.2-Bi0.9I0.1 - up to 2.5 at.% Te
[en] Present article is devoted to deep bismuth purification in rotating container in an oxidizing atmosphere. The targeted deletion of admixtures by means of appropriate chemical treatment of alloy and further carry-over of persistent compounds on surface of ingot was conducted.