Effects of field cooling on low-field microwave absorption in copper oxide superconductors

Abstract

Nonresonant direct absorption of unmodulated microwaves by both the thallium and yttrium copper oxide superconductors exhibits pronounced temperature-and/or field-history dependence. Zero-fieldcooled samples exhibited an absorption minimum at zero field, and this rninimurn was displaced from zero for field-cooled samples. Rotating the samples relative to the field direction caused the minimum to shift in an approximately cosinusoidal manner.

Spectroscopic properties

“…Zero-field-cooled samples exhibit a minimum absorption at zero field; stored flux shifts this minimum in field-cooled samples (Mzoughi et al, 1992).…”