Superconductive spin-valve effect in CoFeHf/Pb/CoFeHf layered structures
I. Physikalisches Institut, Universität Göttingen - Friedrich-Hund Platz 1, D-37077 Göttingen, Germany, EU
Accepted: 22 July 2010
(CoFe)75Hf25/Pb/(CoFe)75Hf25 spin-valve–like structures were investigated to show an influence from the relative orientation of ferromagnetic layers on the superconductivity of the Pb space layer, where (CoFe)75Hf25 is amorphous and thus soft ferromagnetic. The Pb layer deposited at 77 K is super smooth as indicated by X-ray diffraction. A proximity effect arises from the ferromagnetic layers and destroys the superconductivity of Pb with a layer thickness ds<35 nm. In order to minimize the proximity effect, thin oxide layers of CoFeHfO (1 nm) were inserted at relevant interfaces. The superconductivity of Pb is alive then even for layered samples with ds=4 nm, showing a sharp superconductive transition at the critical temperature Tc=6 K. A shift of ΔTc∼30 mK was observed by switching the ferromagnetic layers from parallel to antiparallel.
PACS: 74.45.+c – Proximity effects; Andreev reflection; SN and SNS junctions / 74.78.Fk – Multilayers, superlattices, heterostructures / 85.25.Am – Superconducting device characterization, design, and modeling
© EPLA, 2010