Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 17: Postersitzung II: Transport, Quantenkoh
ärenz, Quantenflüssigkeiten

TT 17.10: Poster

Dienstag, 9. März 2004, 14:30–19:00, Poster A

Conductance Measurements on Ferromagnetic Breakjunctions — •C. Bacca , R. Arnold, and E. Scheer — Department of Physics, University of Konstanz

We investigate lithographically fabricated breakjunctions of ferromagnetic (Co,Ni) nanobridges with or without superconducting leads (Al). With the help of a three-point bending mechanism, the bridges can be opened to a single-atom contact, broken to a vacuum-tunnel contact and closed again repeatedly at low temperatures. As reported for nonmagnetic materials [1] we observe steps in the conductance that are due to atomic rearrangements in the contact region. From the opening and closing curves with and without magnetic field we calculate conductance histograms in order to determine the preferred conductance values. We do not find indications of maxima at half-integer conductance quanta e²/h. The latter is often assumed to give indications for the existence of spin-polarized conductance channels.

We observe very high magnetoconductance effects up to 150% for single-atom or 500% tunnel contacts in magnetic fields up to 5 T. However the details of the magnetoconductance curves are not very reproducible.

[1] J.M. Krans et al. Nature 375, 767 (1995)