Superconducting Transitions of Thin Al Films under the Spin Paramagnetic Limitation

Abstract

The first order transition of superconductivity was confirmed in the vicinity of the spin paramagnetic limit for thin Al films with a thickness less than 60 Å by observing the hysteresis in the resistive transition around 4 T and below 0.6 K.
In the reentrant superconducting state for films thicker than 60 Å, tunneling characteristics of Al-Oxide-Ag junctions under high magnetic fields were found to have higher conductances at low bias voltages than those in the normal state. This supports Fulde’s prediction that the reentrant superconducting state has a higher entropy than the normal state.