Thermal Release of Hidden Magnetic Moments in High T c Bi:2223/Ag Superconducting Tape During Warming to T c

Abstract

We report on measurements of the evolution of the magnetization 〈M〉, upon warming from T 0 (77 K) to T c , for Bi:2223/Ag tape prepared by the continuous filling and forming (CTFF) with the locus of 〈M〉 initially situated along bridges between the envelopes of the major hysteresis curves. Concentric, oppositely directed magnetic moments coexist in the specimens when 〈M〉 lies along the bridges. We focused on the cases where 〈M〉=0, hence before warming, the constituent moments cancel each other exactly. Since they diminish in magnitude at different rates as T is increased to T c , their sequential “release” leads to a rich variety of phenomena. A comparison of experimental and theoretical results shows that our simple model semiquantitatively reproduces the major features of the observations on the specimen of Bi:2223/Ag tape.