Linear temperature dependence of lower critical field inMgB2

Abstract

The lower critical field H c1 has been carefully measured on a well-shaped cylindrical dense sample of the new superconductor MgB 2 fabricated by high-pressure synthesis. The penetration depth is calculated from the H c1 data. It is found that a linear relation of H c1 (T) appears in the whole temperature region below T c . Furthermore, a finite slope of dH c1 /dT and d(T)/dT remains down to the lowest temperature ͑2 K͒. These are inconsistent with the expectation for an isotropic s-wave superconductivity in MgB 2 .

Field-induced suppression of the π-band superconductivity and magnetic hysteresis in the microwave surface resistance of MgB2at temperatures nearTc

“…From figure 6(a), one can see that H p exhibits a linear temperature dependence down to low temperatures, consistently with results in MgB 2 samples reported by different authors [33][34][35]. As is known, the first-penetration field may differ from H c1 if demagnetization and/or surface-barrier effects come into play; however, our results are consistent with the lower critical field for MgB 2 bulk samples reported in the literature [35].…”

Study on the Preparation and Characterizations of an Improved Porous Ti/TiO2/CdS‐CNT/C3N4 Photoelectrode and Photoelectric Catalytic Degradation of Methylene Blue

“…Apparently, the oxidation‐reduction properties of the electrodes are slightly similar. An oxidation peak appeared in the anodic branch of the curve, which implied that TiO 2 , CdS and C 3 N 4 could carry out redox reaction between 0 and 0.25 V. The oxidation peak current of Ti/TiO 2 /CdS‐CNT/C 3 N 4 electrode is higher than the other two electrodes, indicating that the PEC activity of C 3 N 4 is better than CdS and TiO 2 , which further verified the previous literature ,. Additionally, the CNT‐modified interlayer can increase the oxidation ability and catalytic activity of the electrodes …”

Microwave surface resistance in MgB2

“…This behaviour should be reflected in the temperature dependence of the field penetration depth λ(T). However, both linear [19], and quadratic [20] temperature dependence of λ(T) have been reported. The former was extracted from H c1 (T) (measured on bulk polycrystalline rods) and the latter from µSR and acsusceptibility data.…”