Flux Flow and Irreversible Effects
Historically, the term "hysteresis" or "irreversible effect" was first used in the 1930s when it was found that in a certain class of superconductors the Meissner effect did not occur. In the so-called "hard" superconductors, mostly alloys and intermetallic compounds, flux penetrated gradually over a wide range of magnetic fields and in reversing the field most of the flux remained frozen in the specimen. Basic understanding of the irreversible behavior of hard superconductors was afforded by the tube-magnetization experiments of Kim et al. In their experiments the magnetic field H' in a superconducting tube is measured as the externally applied field H is varied. In treating the flux flow it was assumed that the voltage observed in the resistive state of a type II superconductor arises from the motion of vortex lines and that this voltage can be determined by the induction argument.