Measurement of nonlocal conductance in superconductor-ferromagnet hybrid structures

•Detlef Beckmann1, Heiko B. Weber1 und Hilbert v. Löhneysen2,3
1Forschungszentrum Karlsruhe, Institut für Nanotechnologie
2Forschungszentrum Karlsruhe, Institut für Festkörperphysik
3Physikalisches Institut, Universität Karlsruhe

We have measured the conductance of nonlocal aluminum-iron spinvalve structures fabricated by e-beam lithography and shadow evaporation. The sample geometry consists of an aluminum wire with two or more ferromagnetic wires forming diffusive point contacts to the aluminum at varying distances from each other. In the normal state of aluminum, we observe a spin-valve signal which allows us to control the relative orientation of the magnetizations of the ferromagnetic contacts. In the superconducting state, at low temperatures and excitation voltages well below the gap, we observe a spin-dependent non-local conductance which decays on a smaller length scale than the normal-state spin-valve signal. The sign, magnitude and decay length of this signal is consistent with predictions made for crossed Andreev reflections [1] (CARE) in a diffusive superconductor.

[1] G. Deutscher and D. Feinberg, Appl. Phys. Lett. 76 (2000) 487, D. Feinberg, cond-mat/0307099.