Penetration depth of Cooper pairs in the IrMn antiferromagnet

Abstract

Suppression of superconductivity due to the proximity effect between a superconductor and a ferromagnet can be partially alleviated when a Cooper pair simultaneously samples different directions of the short-range exchange field. The superconductor's critical temperature, T C , is therefore expected to partially recover when the ferromagnet is in a multidomain state, as opposed to a single-domain state. Here, we discuss series of experiments performed with ferromagnet(Pt/Co)/spacer(IrMn and Pt)/superconductor(NbN) heterostructures. By tuning the various parameters in play, e.g., superconducting coherence length-to-thicknesses ratio, and domain sizes, we obtained up to 10% recovery of the superconducting critical temperature T C /T C . This large-scale recovery made investigations possible. In particular, from the spacer thickness dependence of T C /T C , it was possible to deduce the characteristic length for Cooper pair penetration in an IrMn antiferromagnet. This information is crucial for electronic transport, and up to now has been difficult to access experimentally for antiferromagnets.

Néel proximity effect at antiferromagnet/superconductor interfaces

“…Furthermore, employing the two-sublattice quasiclassical Green's functions theory developed, our analysis reveals the effect of disorder on all these mechanisms. This seemingly complete picture allows us to envisage the various competing effects taking place in a realistic AF/S bilayer [19,[22][23][24].…”

“…Several experiments have found that AFs lower the critical temperature of an S layer [19,[22][23][24], despite the no net spin-splitting argument above. In some cases, the effect has been comparable to or even larger than that induced by a ferromagnet layer [23].…”

“…Thus, the role of disorder in proximity effect with an AF can be positive or negative on the superconductivity. These competing effects further allow maxima to be feasible in experiments [22][23][24].…”