Manifestation of New Interference Effects in Superconductor/Ferromagnet Spin Valve

Superconductor/ferromagnet (S/F) spin valve effect theories based on the S/F proximity phenomenon assume that the superconducting transition temperature Tc of F1/F2/S or F1/S/F2 trilayers for parallel magnetizations of the F1- and F2-layers (TcP) are smaller than for the antiparallel orientations (TcAP). Here, we report for CoOx/Fe1/Cu/Fe2/In multilayered systems with varying Fe2-layer thickness the sign-changing oscillating behavior of the spin valve effect \Delta Tc=TcAP-TcP. Our measurements revealed the full direct spin valve effect with TcAP>TcP for Fe2-layer thickness dFe2<1 nm and the full inverse (TcAP=1 nm. Interference of Cooper pair wave functions reflected from both surfaces of the Fe2-layer appear as the most probable reason for the observed behavior of \Delta Tc.Comment: Accepted for publication in PR

The Kursk submarine disaster in view of resilience assessment

In August 12, 2000, the Russian Oscar-class submarine Kursk (K-141) sank during a navy manoeuvre in the Barents Sea killing all 118 personnel on board. The vessel was powered by two nuclear reactors and carry nuclear missiles which can be armed. The disaster is well documented and encompasses many socio-technical elements influencing the sequence of events finally leading to wreckage. For this, the disaster is considered as an archetypical event which might highlight the advantages as well as the limitations of resilience assessment approaches, e.g. in comparison with established risk assessment methodology. For this the paper starts with results of a literature survey with resilience metrics and areas of technical applications. The Kursk disaster is reviewed by available literature and research reports by Root Cause Analysis. The causing aspects (events, procedures, human factors, etc.) are then structured and classified according to their relevance and impact on vessel’s resilience. In a next step, these aspects are contrasted to the risk assessment approach as defined, e.g. by ISO 31000. The methodological juxtaposition is intended to characterize the maturity level of resilience analysis in a real world framework as well as to elaborate major differences in validity of the underlying system analysis concepts. Finally, the pros and cons of the reviewing approach are discussed

Full spin switch effect for the superconducting current in a superconductor/ferromagnet thin film heterostructure

Superconductor/ferromagnet (S/F) proximity effect theory predicts that the superconducting critical temperature of the F1/F2/S or F1/S/F2 trilayers for the parallel orientation of the F1 and F2 magnetizations is smaller than for the antiparallel one. This suggests a possibility of a controlled switching between the superconducting and normal states in the S layer. Here, using the spin switch design F1/F2/S theoretically proposed by Oh et al. [Appl. Phys. Lett. 71, 2376 (1997)], that comprises a ferromagnetic bilayer separated by a non-magnetic metallic spacer layer as a ferromagnetic component, and an ordinary superconductor as the second interface component, we have successfully realized a full spin switch effect for the superconducting current.Comment: 5 pages, 4 figure

Critical Temperature Oscillations and Reentrant Superconductivity due to the FFLO like State in F/S/F Trilayers

Ferromagnet/Superconductor/Ferromagnet (F/S/F) trilayers, in which the establishing of a Fulde-Ferrell Larkin-Ovchinnikov (FFLO) like state leads to interference effects of the superconducting pairing wave function, form the core of the superconducting spin valve. The realization of strong critical temperature oscillations in such trilayers, as a function of the ferromagnetic layer thicknesses or, even more efficient, reentrant superconductivity, are the key condition to obtain a large spin valve effect, i.e. a large shift in the critical temperature. Both phenomena have been realized experimentally in the Cu 41 Ni 59 /Nb/Cu 41 Ni 59 trilayers investigated in the present work.Comment: 22 pages, 6 figure