| Summary: | 博士 === 國立成功大學 === 物理學系碩博士班 === 101 === Both tin and lead are the conventional type I superconductor with critical temperature Tc = 3.72K, 7.20K and critical field Hc = 306,803 Oe respectively. These elements were confined into SiO2 nano-sphere matrices or nanoporous glass, which created Sn opal, Sn in porous glass, Pb opal, and Pb in porous glass respectively. Thermal and magnetic properties of our samples can be measured by heat capacity, ac susceptibility, and dc magnetization. We discovered that the characters of type II superconductor exist in these samples, such as the upper critical field, flux pinning effect, positive curvature, and flux jumps.
The upper critical field higher than critical field of bulk can be estimated by higher fields region of H－Tc diagram, and positive curvature can be observed from lower fields part. The existence of flux pinning effect was proved by M－T measurement. Flux jumps can be observed on hysteresis loops, which were successfully simulated using the adiabatic approximation which was developed for type-II superconductors. Besides, we studied frequency dependence of critical temperatures, and calculated the thermal activation energy at the static fields. We tried to make Pb in porous glass fixed in high pressure cell and measured dc magnetization, which revealed that both critical temperature and critical field lowered under high pressure.
|
|---|
