Dresden 2006 – scientific programme

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TT: Tiefe Temperaturen

TT 21: Transport: Nanoelectronics II - Spintronics and Magnetotransport - Part 2

TT 21.9: Talk

Tuesday, March 28, 2006, 18:30–18:45, HSZ 105

Magnetic Switching of the Superconducting Transition Temperature Ferromagnetic/Superconducting Bi- and Tri-Layers — •Roland Steiner, Alfred Plettl, and Paul Ziemann — Abteilung Festkörperphysik, Universität Ulm, D-89069 Ulm

Superconductivity and ferromagnetism are two antagonistic phenomena. The interplay between these two phenomena in multilayer systems is currently under intensive research [1].

In the present contribution results are presented on the magnetoresistance R(H) of ferromagnet/superconductor double- and trilayer-systems in their superconducting state with a typically 30 nm thick Niobium film as superconductor in all cases. It is demonstrated that the R(H)-curve exhibits a non-monotonous behaviour in the range of the coercitive field H_coe of the involved ferromagnets close to the superconducting transition at T_c. The T_c(H)-curves show a local minimum at H_coe. In contrary to theoretical results based on the Proximity-effect in trilayer systems [2], in the present system, switching into a parallel oriented magnetization of the sandwiching FM-layers leads to a T_c increase (Δ T_c ≈ 50 mK) as compared to the corresponding antiparallel alignement.

Additional experiments on FM/SC double layers deliver clear indications that the observed behaviour can be attributed to stray fields acting on the superconducting Niobium layer. To underline this conclusion micromagnetic simulations (oommf-code) will be discussed.

[1] A. Buzdin, Nat. Mat. (3), 751 (2004)

[2] I. Baladié et al., Phys. Rev. B 63, 54518 (2001)