Paramagnetic Meissner effect in Bi high-temperature superconductors

Abstract

For certain ceramic samples of the Bi-based high-temperture superconductors, the dc-field-cooling signal becomes paramagnetic in fields below a few 100 mOe. This effect correlates with an anomaly in the low-field microwave absorption. The data are consistent with orbital paramagnetic moments due to the appearance of spontaneous supercurrents in fields smaller than the lower critical field ${\mathit{H}}_{\mathit{c}1\mathit{a}}$ parallel to the CuO planes.