Diamagnetic response of mesoscopic superconducting rings aboveTc

Various small effects that might appear to be obstacles in the way of measuring the persistent current in a mesoscopic ring of a superconductor above but close to ${\mathit{T}}_{\mathit{c}}$ are investigated, among them the effect of the magnetic field penetrating into the metal, the Zeeman splitting, and the inductance of the ring. Analogies and differences with a (single-junction) superconducting quantum interference device (SQUID) are pointed out, the differences being due to the high harmonic content of the current flux relation. Typical parameter values make flux trapping virtually impossible.