Superconductive spin-valve effect in CoFeHf/Pb/CoFeHf layered structures

I. Physikalisches Institut, Universität Göttingen - Friedrich-Hund Platz 1, D-37077 Göttingen, Germany, EU

^a yluo@gwdg.de

Received: 30 April 2010
Accepted: 22 July 2010

Abstract

(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 d_s<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 d_s=4 nm, showing a sharp superconductive transition at the critical temperature T_c=6 K. A shift of ΔT_c∼30 mK was observed by switching the ferromagnetic layers from parallel to antiparallel.