Paramagnetic Meissner Eeect in Conventional Nb Superconductors
نویسنده
چکیده
The paramagnetic Meissner eeect (PME), in which the eld-cooled-magnetization (FCM) of superconducting samples is positive below the super-conducting transition temperature T c , has been observed in certain ceramic and single-crystal samples of the high-T c cuprate superconductors and more recently in disk-shaped Nb samples. Through systematic investigations of the conditions for observing the PME in Nb disks, various surface treatments to the Nb disks were found to change both the zero-eld-cooled-magnetization (ZFCM) and the FCM, including the appearance of a positive FCM in samples previously not exhibiting the PME as well as the elimination of the PME through surface abrasion. These results suggest that the PME arises from the eld distributions created by the ux pinning associated with microstructural defects on the surface layer of the disk.
منابع مشابه
Giant paramagnetic Meissner effect in multiband superconductors
Superconductors, ideally diamagnetic when in the Meissner state, can also exhibit paramagnetic behavior due to trapped magnetic flux. In the absence of pinning such paramagnetic response is weak, and ceases with increasing sample thickness. Here we show that in multiband superconductors paramagnetic response can be observed even in slab geometries, and can be far larger than any previous estima...
متن کاملParamagnetic Reentrance Effect in NS Proximity Cylinders
A scenario for the unusual paramagnetic reentrance behavior at ultra-low temperatures in Nb-Ag, Nb-Au, and Nb-Cu cylinders is presented. For the diamagnetic response down to temperatures of the order 15 mK, the standard theory (quasi-classical approximation) for superconductors appears to work very well, assuming that Ag, Au, and Cu remain in the normal state except for the proximity-induced su...
متن کاملDetailed investigation of the superconducting transition of niobium disks exhibiting the paramagnetic Meissner effect
Detailed investigation of the superconducting transition of niobium disks exhibiting the paramagnetic Meissner effect. Abstract The superconducting transition region in a Nb disk showing the para-magnetic Meissner effect (PME) has been investigated in detail. From the field-cooled magnetization behavior, two well-defined temperatures can be associated with the appearance of the PME: T 1 (< T c)...
متن کاملکشف ابررسانایی دمای بالا- کشف غیرمنتظره، رفتار نامتعارف
A brief review on some peculiar properties of high temperature superconductors (HTS) is presented. Twenty years after the discovery, it appears more and more clear that the behaviour of this new class of materials is remarkably different from what have been re-classified as “conventional” superconductors. In the following we will focus our attention on the study of two phenomena, namely the J...
متن کاملParamagnetic Meissner Effect and Strong Time Dependence at High Fields in Melt-Textured High-TC Superconductors
In this work we report on systematic field-cooled magnetization experiments in melt-textured YBa2Cu3O7−δ samples containing Y211 precipitates. Magnetic fields up to 14 T were applied either parallel or perpendicular to the ab planes and a strong paramagnetic response related to the superconducting state was observed. This effect is known as paramagnetic Meissner effect (PME). The magnitude of t...
متن کامل