Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDelta H = Delta B region in volume defect-dominating superconductor
118
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
According to Ginzburg-Landau theory, it has been generally accepted that the diamagnetic property decreases after the lower critical field. However, we found that (Fe, Ti) particle doped MgB2 specimens reveal the Delta H = Delta B section in the magnetization curves, which are not following the theory. We present whether this phenomenon appears to be only confined to (Fe, Ti) particle doped Magnesium diborid superconductor, whether there is a theoretical basis and why it does not appear in other superconductors. We have understood that the cause of the Delta H = Delta B section is the pinning phenomenon of defects in the superconductor and it only occurs in volume defect dominating superconductors. The width of the Delta H = Delta B section along the number of defects and Hc2 was estimated assuming that defects are in the ideal state, and compared with experimental results. We hypothesized that pinned fluxes have to be picked out from the defect and move into an inside of a superconductor regardless free energy depth of the defect if the distance between fluxes pinned at the defect is equal to the one of upper critical field. It is considered that the reason that this phenomenon has not been reported yet is the flux jump of the volume defect dominating superconductor. The section means that the fluxes that have penetrated into a inside of a superconductor in which volume defects exist are preferentially pinned on them over the entire specimen before Ginzburg-Landau behavior. If the size of volume defects is uniform in some extent, the influence of the planar and line defects is small and the flux jump does not occur, we believe that the section must be observed in any superconductor. It is because this is one of the basic natures of pinning phenomenon in the volume defect dominating superconductor.
rate research
Read More
We studied a method of measuring upper critical field (H$_{c2}$) of a superconductor based on the width of $Delta$H = $Delta$B region, which appears in the superconductor that volume defects are many and dominant. Here we present the basic concept and details of the method. Although H$_{c2}$ of a superconductor is fixed according to kind of the superconductor, it is difficult to measure H$_{c2}$ experimentally, and the results are different depending on the experimental conditions. H$_{c2}$ was calculated from the theory that pinned fluxes at volume defects are picked out and move into an inside of the superconductor when their arrangement is the same as that of H$_{c2}$ state of the superconductor. H$_{c2}$ of MgB$_2$ obtained by the method was 65.4 Tesla at 0 K. The reason that H$_{c2}$ obtained by the method is closer to ultimate H$_{c2}$ is based on that $Delta$F$_{pinning}$/$Delta$F$_{pickout}$ is more than 4 when pinned fluxes at volume defects of 163 nm radius are picked out. The method will help to find the ultimate H$_{c2}$ of volume defect-dominating superconductors.
Whereas there are two critical fields that are H$_{c1}$ and H$_{c2}$ in the ideal type II superconductor, there is another critical field H$_{c1}$ defined as the field showing the maximum diamagnetic property in the real type II superconductor. We would present that H$_{c1}$ is able to be proved theoretically and experimentally. We have derived an equation based on flux-pinning effect of volume defects. MgB$_2$ bulks which were synthesized by Mg and B are similar to this model. The number of quantum fluxes pinned at a defect of radius r, a pinning penetration depth, magnetic flux penetration method, and a magnetization at H$_{c1}$ in the static state are suggested through the equation of the model. It was speculated that pinned fluxes at a volume defect in the superconductor have to be pick-out depinned from the defect and move an inside of the superconductor when pick-out forces of pinned fluxes is larger than pinning force of the defect (F$_{pickout}$ $>$ F$_{pinning}$) or when the shortest distance between pinned fluxes at a volume defect is the same as that of H$_{c2}$. In reality, $Delta$G$_{dynamic}$ which is sum of fluxes movement energy and fluxes vibration energy is involved in movement of pinned fluxes. When volume defects are small and many, the number of pinned fluxes at a volume defect calculated by experimental results was closer to that of ideally calculated ones because of a small $Delta$G$_{dynamic}$. However, when volume defects are large and a few, the number of pinned fluxes at a volume defect calculated by experimental results were much fewer than that of ideally calculated ones because of a large $Delta$G$_{dynamic}$.
We report a Cu $K$-edge resonant inelastic x-ray scattering (RIXS) study of charge-transfer excitations in the 2-8 eV range in the structurally simple compound HgBa$_2$CuO$_{4+delta}$ at optimal doping ($T_{rm c} = 96.5 $ K). The spectra exhibit a significant dependence on the incident photon energy which we carefully utilize to resolve a multiplet of weakly-dispersive ($ < 0.5$ eV) electron-hole excitations, including a mode at 2 eV. The observation of this 2 eV excitation suggests the existence of a charge-transfer pseudogap deep in the superconducting phase. Quite generally, our data demonstrate the importance of exploring the incident photon energy dependence of the RIXS cross section.
High stability and oxygen permeability are two prominent requirements for the oxygen transport membrane candidates used as industrialization. Herein, we report several composite membranes based on xwt.%Ce0.9Pr0.1O2(CPO)-(100-x)wt.%Pr0.6Sr0.4Fe0.8Al0.2O3(PSFAO) (x = 50, 60 and 75) prepared via a modified Pechini method. Oxygen permeability test reveals that the 60CPO-40PSFAO composition exhibits the highest oxygen permeability. The oxygen permeation flux through the optimal uncoated 0.33 mm-thickness 60CPO-40PSFAO composite can reach 1.03 mL cm-2 min-1 (over the general requirement value of 1 mL cm-2 min-1) in air/He atmosphere at 1000 {deg}C. In situ XRD performance confirms the optimal 60CPO-40PSFAO sample shows excellent stability in CO2-containing atmospheres. The 60CPO-40PSFAO membrane still exhibits simultaneously excellent oxygen permeability and phase stability after operating for over 100 h at air/CO2 condition at 1000 {deg}C, which further indicates that the 60CPO-40PSFAO composite is likely to be used for oxygen supply in CO2 capture
The compound HgBa$_2$CuO$_{4+Delta}$ (Hg1201) exhibits a simple tetragonal crystal structure and the highest superconducting transition temperature (T$_c$) among all single Cu-O layer cuprates, with T$_c$ = 97 K (onset) at optimal doping. Due to a lack of sizable single crystals, experimental work on this very attractive system has been significantly limited. Thanks to a recent breakthrough in crystal growth, such crystals have now become available. Here, we demonstrate that it is possible to identify suitable heat treatment conditions to systematically and uniformly tune the hole concentration of Hg1201 crystals over a wide range, from very underdoped (T$_c$ = 47 K, hole concentration p ~ 0.08) to overdoped (T$_c$ = 64 K, p ~ 0.22). We then present quantitative magnetic susceptibility and DC charge transport results that reveal the very high-quality nature of the studied crystals. Using XPS on cleaved samples, we furthermore demonstrate that it is possible to obtain large surfaces of good quality. These characterization measurements demonstrate that Hg1201 should be viewed as a model high-temperature superconductor, and they provide the foundation for extensive future experimental work.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
