Inverse magnetic proximity effect in superconducting Sn/Ni nanopomposites

• Main Authors: Yen-Cheng Chen, 陳彥呈
• Other Authors: Wen-Hsien Li
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/08991602461363855189

碩士 === 國立中央大學 === 物理研究所 === 100 === In this thesis, we discuss the superconducting proximity effect in Sn/Ni nanocomposites which is the mixture of Sn and Ni nanoparticles with different mass ratios and packing fractions. The nanoparticles are fabricated by thermal vapor deposition method and are characterized by X-ray diffraction patterns. The average diameters of Sn/Ni are 10/5 nm with FWHM 8.1/4.4 nm. In our study, the superconducting diamagnetic screening effect was measured through AC magnetic susceptibility (χ_ac=χ’ +iχ’’). The temperature dependence of in-phase component χ’(T) can be described by the Scalapino’s expression, which allows extracting the superconducting transition temperature. There is an unconventional enhancement of critical temperature (TC) in the regime of 7.5%~15% of the Ni mass composition. It is observed that an abnormal magnetic behaviors which is so-called inverted hysteresis loops or negative remanence magnetization in the Sn/Ni nanocomposites. The qualitatively analysis was done and a model was given to describe the phenomenon.