Probing the origin of the superconducting spin-valve effect

Inter-layer magnetic exchange coupling is the key control mechanism underpinning spintronics and is often coupled to other spintronic effects, such as giantmagnetoresistance(GMR) and spin transfer torques. Recently, Zhu et al. reported a new class of inter-layer exchange coupling, a kind of RKKY coupling through a superconducting spin-valve structure. They observed a GMR-like response with an infinite MR ratio because of the zero resistance in the superconducting state. One of the conclusions presented in the paper is: 'the behaviour reported here cannot be explained on the basis of any conventional exchange coupling'. With our PNR+PA measurements we were able to gain a detailed understanding of the magnetic state in the superconducting phase but to clarify the influence of the superconductor itself a scan through the superconducting transition is essential.