1,720,971 research outputs found
A new method to detect the vortex glass phase and its evidence in YBCO
No full textThe evidence of the vortex glass phase has been obtained by analysing the nonlinear magnetic response of type-II superconductors. The method introduced here is based on a combined frequency dependence analysis of the real and imaginary part of the 1st and 3rd harmonics of the AC magnetic susceptibility. The analysis has been performed by taking into account both the components and the Cole-Cole plots (i.e. the imaginary part as a function of the real part). Numerical simulations have been used to identify the fingerprints of the magnetic behaviour in the vortex glass phase. These characteristics allowed the vortex glass phase to be distinguished from the other disordered phases, even those showing similar electrical properties. Finally, this method has been successfully applied to detecting the vortex glass phase in an YBCO bulk melt-textured sample
Response of Glass and Liquid Phases in the Vortex lattice to an external AC magnetic field at different frequencies
No full textWe individuated a method to distinguish a glass phase from a highly viscous liquid phase in a lattice of vortices, established in type-two superconductors. Our analysis is based on the study of the temperature dependence of numerically obtained 1st and 3rd harmonics curves of the AC magnetic susceptibility, by changing the frequency of the applied AC magnetic field. The harmonics are obtained by integrating the non-linear diffusion equation for the magnetic field, with different voltage–current characteristics, corresponding to the two different phases. This method could be applied to the analysis of experimental curves in order to determine if the detected magnetic response of superconducting samples may be interpreted in terms of vortex glass or Kim–Anderson model
Cole-Cole plots of the 1st and the 3rd harmonics of the AC susceptibility for the study of dissipative phenomena in type II superconductors
No full textThird harmonics of the AC magnetic susceptibility: a method for the study of flux dynamics in high temperature superconductors
No full textThe temperature dependence of the 1st and 3rd harmonics ( ) of the AC magnetic susceptibility has been measured on melt grown YBCO samples for different frequencies and amplitudes of the AC magnetic field and intensity of a contemporaneously applied DC field. With the help of critical state models and of numerical simulations [22], we have devised a novel method, based on the combined analysis of the 1st and the 3rd harmonics (specifically on the comparison between and ), that allows to distinguish different temperature ranges dominated by the different dissipative magnetic flux regimes. In particular, we identified three principal “zones” in the temperature dependence of the real part of the 3rd harmonic: the “zone 1”, in the temperature range below the peak of the imaginary part of the 1st harmonic, , and the “zone 2”, characterized by negative values in a temperature region just above , both dominated by the creep regime; the zone 3, just below T c , in which we revealed the presence of Thermally Assisted Flux Flow (TAFF). By the identification of these “zones”, an estimation of the value of the pinning potential can be obtained. Copyright Springer-Verlag Berlin/Heidelberg 2003
Effect of the amplitude of the AC magnetic field on the vortex dynamics: a quantitative analysis in Nb and NbTi polycrystalline samples.
No full textInvestigations of magnetic behaviour in various type of Nb3Sn multifilamentary wires by means of the 1st and 3rd harmonics of the AC magnetic susceptibility
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H(T) Phase Diagram in Nb3Sn: A Different Behavior in Single Crystals, Polycristalline Samples and Multifilamentary Wires
No full textLight the world and change its color: A case study in Italian secondary school using IBSE methodology
No full textWhat color is it? It is not a trivial question: answer depends on the lamp used to light the world! Let's fix a light and measure with our human instruments, eyes and ears, a colored and orchestral environment: may we distinguish, at the same time, all the colors and sounds? Here we show a case study using Inquiry Based Science Education (IBSE), a teaching methodology, focused on the wave-matter interaction in daily experience and some ways to detect it by our senses. IBSE methodology engages students eliciting investigation of physical phenomena. General expected outcomes are an improvement of students' motivation and a more successful learning experience. We planned an educational path, based on investigation, for students attending the first year of high school. The course has been developed in four lessons (2.5 hours each) for a total of 10 hours. This path has been experimented in four different parallel classes. In each class, students have been divided into 5 or 6 groups. The first phase, "engage", is a simple trick: try to guess the color of four cards lighted with a monochromatic beam, red, blue, or green, in the dark. Once a white light is turned on, students will be surprised to see the true colors of the cards. After this "engagement", students "explore" interaction between wave and matter, accomplishing some tasks and trying to "explain" the observed phenomena. The third and most important step is to "extend": students directly experience additive color synthesis, with attention to pointillism, to subtractive color synthesis, and to superposition of sound. Later, each group, as in a flipped lesson, looks for answers to preliminary questions, by investigation: ear and eye behaviour, differences between electromagnetic and sound waves, electromagnetic spectrum. ICT is a valuable support in this phase. A multimedia product is requested at the end of investigation. In order to "evaluate" this educational path, it has been proposed to think about the use of a monochromatic lamp to change a colored word in another one, without some yellow and red letters. A feedback questionnaire has been also used to evaluate the educational path. The results of the questionnaire show that students are satisfied with this new methodology and activities. Satisfactory results, however, depend upon teacher's ability to motivate all students in attending classes
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