Observations and Analysis of the Thermal Disclosure of Hidden Magnetic Moments in High T c Bi:2223/Ag Tape During Warming from Low Temperatures (20, 30, and 50 K) to T c:H ⊥ c Axis

Abstract

We report on measurements of the evolution of the magnetization 〈M〉 upon warming from T 0 (20, 30, 50 K) to T c, for Bi:2223/Ag tape prepared by the continuous filling and forming (CTFF) with the magnetization 〈M〉 initially situated along bridges between the envelopes of the major hysteresis curves. We focused on the cases where 〈M〉=0, the constituent moments cancel each other exactly. We have measured the release of magnetic moments as a function of temperature. 〈M〉 versus T traces S shaped curves where after tracing a valley the paramagnetic magnetization is followed by the appearance of a diamagnetic peak, which is then extinguished as T attains T c. Our observations, evidence for hidden magnetization, have been explained on the basis of the critical state model assuming certain dependence of the critical current density and Meissner surface current on temperature.