Results 1 - 10 of 5246
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[en] We investigate the upper critical field anisotropy ΓH and the magnetic penetration depth anisotropy Γλ of a high-quality FeSe1-x single crystal using angular dependent resistivity and torque magnetometry up to 14 T. High quality single crystals of FeSe1-x were successfully grown using KCl-AlCl3 flux method, which shows a sharp superconducting transition at TC ⁓ 9 K and a high residual resistivity ratio of ⁓ 25. We found that the anisotropy ΓH near TC is a factor of two larger than found in the poor-quality crystals, indicating anisotropic 3D superconductivity of FeSe1-x. Similar to the 1111-type Fe pnictides, the anisotropies Γλ and ΓH show distinct temperature dependence; ΓH decreases but Γλ increases with lowering temperature. These behaviors can be attributed to multi-band superconductivity, but different from the case of MgB2. Our findings suggest that the opposite temperature dependence of Γλ and ΓH is the common properties of Fe-based superconductors.
[en] Moving vortex lattice in type-II superconductors can result in the radiation of electromagnetic waves in the range of terahertz frequency. The vortex flow dynamics in superconductors follow the London equation. In this paper, the effects of the superconductor coherence length and the London penetration depth on the radiated power is investigated by solving the London equation in the presence of vortices. The results show that by decreasing the coherence length, the radiation power will significantly increase. Also, it is possible to obtain more radiated power with a sharp peak by increasing the penetration depth. Further investigation of the effect of Joule heating reveals that radiation power is almost independent of temperature when we are far from critical temperature. But on the other hand, near the critical temperature, the radiation power is strongly dependent on the temperature variation. Also, by increasing the bias current, the radiation power will augment, and the frequency of radiated peaks will change accordingly. (paper)
[en] We discuss the Meissner response to a known field source of superconductors having inhomogeneities in their penetration depth. We simplify the general problem by assuming that the perturbations of the fields by the penetration depth inhomogeneities are small. We present expressions for inhomogeneities in several geometries, but concentrate for comparison with experiment on planar defects, perpendicular to the sample surfaces, with superfluid densities different from the rest of the samples. These calculations are relevant for magnetic microscopies, such as Scanning Superconducting Quantum Interference Device (SQUID) and Magnetic Force Microscope, which image the local diamagnetic susceptibility of a sample.
[en] We compare the temperature dependences of the in-plane London penetration depth (Δλab(T)) for several Ba(Fe1-xTMx)2As2 (TM = Co, Ni, Pd, Co + Cu) superconductors at high concentration of electrons, ne, added per Fe site. We show that regardless of the transition metal TM, for ne ≥ 0.12, the penetration depth has a power-law temperature dependence ΔλL(T)∝Tn, but with the exponent n∼1.65, thus significantly lower than the value n ≥ 2 previously reported for lower electron concentrations. On doping with electrons from the 3d shells, the magnitude of the variation with temperature of ΔλL(T) is larger for Ni substitution than for Co substitution, and larger for Co + Cu co-doping than for Ni co-doping. However, comparing the effect of 3d and 4d electrons, for the isovalent elements Ni and Pd respectively, we found that the rates of change in penetration depth with temperature are nearly identical for the two compounds.
[en] The values of the superconducting penetration depth measured on thin and thick niobium films are presented. The obtained values of s.p.d. in our experiments at T=4.9 K are 145(+/-15) nm for a thin film and 90 (+/-) nm for a thick film. It is essentially different from that one for bulk niobium. 4 refs.; 1 fig
[en] The complex conductivity of a MgB2 film has been investigated in the frequency range 4<ν<30 cm-1 and for temperatures 2.7< T<300 K . The overall temperature dependence of both components of the complex conductivity is reminiscent of BCS-type behavior, although a detailed analysis reveals a number of discrepancies. A peak in the temperature dependence of the real part of the conductivity is detected for frequencies below 9 cm-1 . The superconducting penetration depth follows a T2 behavior at low temperatures
[en] The capacity and applicability of the organic-inorganic synthesized penetration-reinforcing agent that was developed with the purpose of preventing aging and improving durability in concrete structures as their number of years in service increased were proven through experimental methods. The developed organic-inorganic penetrationre-inforcing agent creates the effect of increasing compressive strength as well as produces higher durability against the aging factors of the environment
[en] After that the decontamination substance has been applied to the contaminated surface, a microwave field is applied, in order to enhance the penetration of the decontaminating substance and the dissolution of the contaminated surface. In this way, the time needed for decontamination can be shortened, and he amount of decontamination substance reduced
[en] Highlights: • Non-monotonic dependence of penetration depth on the impact velocity is observed. • Alekseevskii-Tate model is better in predicting the non-monotonic eroding penetration depth. • Judgement criterion for the occurrence of the non-monotonic dependence is proposed. Terminal ballistic performance of high-strength projectiles penetrating into metallic targets is mostly concerned by both weapon and armor designers. Most existing works are concentrated on the rigid-eroding penetration regime, and limited studies have addressed the rigid-deforming-eroding penetration regime. In this paper, nineteen shots of hemispherical nosed D6A steel projectiles penetration test on 5A06-H112 aluminum targets is conducted with a wide range of velocities (696 m/s–1870 m/s). The non-monotonic dependence of depth of penetration (DOP) on the impact velocity is observed, which successively corresponds to the three penetration stages, i.e., rigid projectile penetration, deforming projectile penetration without eroding and eroding projectile penetration. Then, for the non-monotonic rigid-deforming-eroding projectile penetration regime, the applicability of the existing six classical theoretical models for both rigid and eroding projectile penetrations is evaluated. Furthermore, the transition velocities (the upper limit of rigid penetration and the lower limit of eroding penetration) are discussed and an empirical judgement criterion for the occurrence of non-monotonic dependence is proposed. Finally, by conducting the dynamic compression test, quasi-static tension test under varying temperature, etc., the Johnson-Cook model parameters for the present target and projectile are calibrated and validated by numerically simulating the present test.