Paramagnetic Meissner effect in multiply-connected superconductors

TitleParamagnetic Meissner effect in multiply-connected superconductors
Publication TypeJournal Article
Year of Publication2000
AuthorsNielsen, A. P., Cawthorne A. B., Barbara P., Wellstood F. C., Lobb C. J., Newrock R. S., and Forrester M. G.
JournalPhysical Review B
Volume62
Pagination14380-14383
Abstract

We have measured a paramagnetic Meissner effect in Nb-Al2O3-Nb Josephson-junction arrays using a scanning superconducting quantum interference device microscope. The arrays exhibit diamagnetism for some cooling fields and paramagnetism for other cooling fields. The measured mean magnetization is always small, < Phi (tot) - Phi (ext)> < 0.3(0) tin terms of flux per unit cell of the array, where Phi (0) is the flux quantum), for the range of cooling fields investigated (- 12 Phi (0) to 12 Phi (0)). We demonstrate that a different model of magnetic screening, valid for multiply-connected superconductors, reproduces all of the essential features of paramagnetism that we observe and that no exotic mechanism, such as d-wave superconductivity, is needed for paramagnetism.