Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userInfluence of carbon-ion irradiation on the superconducting critical properties of MgB$_2$ thin films
146
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We investigate the influence of carbon-ion irradiation on the superconducting critical properties of MgB$_2$ thin films. MgB$_2$ films of two thicknesses viz. 400 nm (MB400nm) and 800 nm (MB800nm) were irradiated by 350 keV C ions having a wide range of fluence, 1 x 10$^{13}$ - 1 x 10$^{15}$ C atoms/cm$^2$. The mean projected range ($R_p$) of 350 keV C ions in MgB$_2$ is 560 nm, thus the energetic C ions will pass through the MB400nm, whereas the ions will remain into the MB800nm. The superconducting transition temperature ($T_c$), upper critical field ($H_{c2}$), $c$-axis lattice parameter, and corrected residual resistivity ($rho_{corr}$) of both the films showed similar trends with the variation of fluence. However, a disparate behavior in the superconducting phase transition was observed in the MB800nm when the fluence was larger than 1 x 10$^{14}$ C atoms/cm$^2$ because of the different Tcs between the irradiated and non-irradiated parts of the film. Interestingly, the superconducting critical properties, such as $T_c$, $H_{c2}$, and $J_c$, of the irradiated MgB$_2$ films, as well as the lattice parameter, were almost restored to those in the pristine state after a thermal annealing procedure. These results demonstrate that the atomic lattice distortion induced by C-ion irradiation is the main reason for the change in the superconducting properties of MgB$_2$ films.
rate research
Read More
The superconducting and critical current properties of thin films of NiBi3 formed on the surface of carbon microfibers and sapphire substrates are reported. The NiBi3 coated carbon microfibers were prepared by reacting 7 {mu}m diameter Ni-coated (~ 80 nm) carbon fibers with Bi vapor, and thin films on sapphire were formed by exposing electron-beam deposited Ni films (~ 40 - 120 nm) to Bi vapor. The microfibers and films show Tc = 4.3 K and 4.4 K,respectively, which were slightly higher than that reported for bulk polycrystalline NiBi3. The critical current density (Jc) was measured below the transition temperature and is well described by the Ginzburg-Landau power-law.
We present experimental results of the upper critical fields $H_{rm c2}$ of various MgB$_2$ thin films prepared by the molecular beam epitaxy, multiple-targets sputtering, and co-evaporation deposition apparatus. Experimental data of the $H_{rm c2}(T)$ are successfully analyzed by applying the Gurevich theory of dirty two-band superconductivity in the case of $D_{pi}/D_{sigma}>1$, where $D_{pi}$ and $D_{sigma}$ are the intraband electron diffusivities for $pi$ and $sigma$ bands, respectively. We find that the parameters obtained from the analysis are strongly correlated to the superconducting transition temperature $T_{rm c}$ of the films. We also discuss the anormalous narrowing of the transition width at intermediate temperatures confirmed by the magnetoresistance measurements.
FeSe0.5Te0.5 thin films were grown by pulsed laser deposition on CaF2, LaAlO3 and MgO substrates and structurally and electro-magnetically characterized in order to study the influence of the substrate on their transport properties. The in-plane lattice mismatch between FeSe0.5Te0.5 bulk and the substrates shows no influence on the lattice parameters of the films, whereas the type of substrates affects the crystalline quality of the films and, therefore, the superconducting properties. The film on MgO showed an extra peak in the angular dependence of critical current density Jc({theta}) at {theta} = 180{deg} (H || c), which arises from c-axis defects as confirmed by transmission electron microscopy. In contrast, no Jc({theta}) peaks for H || c were observed in films on CaF2 and LaAlO3. Jc({theta}) can be scaled successfully for both films without c-axis correlated defects by the anisotropic Ginzburg-Landau (AGL) approach with appropriate anisotropy ratio {gamma}J. The scaling parameter {gamma}J is decreasing with decreasing temperature, which is different from what we observed in FeSe0.5Te0.5 films on Fe-buffered MgO substrates.
The electronic properties of the carbon substituted MgB$_2$ single crystals are reported. The carbon substitution drops T$_c$ below 2 K. In-plane resistivity shows a remarkable increase in residual resistivity by C-substitution, while the change of in-plane/out-of-plane Hall coefficients is rather small. Raman scattering spectra indicate that the E$_{2g}$-phonon frequency radically hardens with increasing the carbon-content, suggesting the weakening of electron-phonon coupling. Another striking C-effect is the increases of the second critical fields in both in-plane and out-of-plane directions, accompanied by a reduction in the anisotropy ratio. The possible changes in the electronic state and the origin of T$_c$-suppression by C-substitution are discussed.
In this paper we explore the effects of 3.5 MeV proton irradiation on Fe(Se,Te) thin films grown on CaF2. In particular, we carry out a systematic experimental investigation with different irradiation fluences up to 7.30x10^16 cm^-2 and different proton implantation depths, in order to clarify whether and to what extent the critical current is enhanced or suppressed, what are the effects of irradiation on the critical temperature, the resistivity and the critical magnetic fields, and finally what is the role played by the substrate in this context. We find that the effect of irradiation on superconducting properties is generally small as compared to the case of other iron-based superconductors. Such effect is more evident on the critical current density Jc, while it is minor on the transition temperature Tc, on the normal state resistivity and on the upper critical field Hc2 up to the highest fluences explored in this work. In addition, our analysis shows that when protons implant in the substrate far from the superconducting film, the critical current can be enhanced up to 50% of the pristine value at 7 T and 12 K, while there is no appreciable effect on critical temperature and critical fields together with a slight decrease in resistivity. On the contrary, when the implantation layer is closer to the film-substrate interface, both critical current and temperature show a decrease accompanied by an enhancement of the resistivity and the lattice strain. This result evidences that possible modifications induced by irradiation in the substrate may affect the superconducting properties of the film via lattice strain. The robustness of the Fe(Se,Te) system to irradiation induced damage makes it a promising compound for the fabrication of magnets in high-energy accelerators.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
