Penetration depth of Cooper pairs in the IrMn antiferromagnet

Abstract

Suppression of superconductivity due to proximity effects between a superconductor and a ferromagnet can be partially lifted when different directions of the short-range exchange field are sampled simultaneously by a Cooper pair. Partial recovery of the superconducting critical temperature, ΔTC, is therefore expected when the ferromagnet is set in a multi-domain state compared to a single domain state [1-3]. Here, we discuss series of experimental results for ferromagnet(Pt/Co)/spacer(IrMn)/superconductor(NbN) heterostructures [4]. By tuning the various parameters into play, e.g. superconducting coherence length-to-thicknesses ratio, and domain sizes, we obtained a recovery of the superconducting critical temperature ΔTC/TC as large as 10% (Fig. 1(a,b)). Such a large scale of ΔTC/TC opened the pathway for novel investigations. In particular, from the spacer thickness-dependence of ΔTC/TC, characteristic length for Cooper pair penetration (ξIrMn ~ 6.7 nm) (Fig. 1(c)) was deduced in the IrMn antiferromagnet [4]. It is a crucial information for electronic transport, which are currently difficult to access experimentally for antiferromagnets [5]. **