Suppression of magnetic coupling in superconducting GdN-NbN-GdN trilayers

Abstract

We report on the effect of superconducting ordering in an NbN spacer layer on the magnetic coupling behavior in GdN-NbN-GdN trilayers. In the normal state of NbN, the weak ferromagnetic semiconductor GdN layers were found to be antiferromagnetically coupled, as inferred from magnetization measurements. A gradual decrease in the coupling strength was observed on cooling through T c. Although this is to be expected, due to a decrease in the quasiparticle density of states (due to Cooper pairing), there has been no experimental confirmation so far. The gradual decrease in coupling strength above Tc correlates well with the appearance of superconducting fluctuations in the spacer NbN layer.