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TT: Tiefe Temperaturen

TT 26: Transport - Poster Session

TT 26.2: Poster

Mittwoch, 29. März 2006, 14:30–18:30, P1

Conductance Measurements on Ferromagnetic Breakjunctions — •Magdalena Hüfner, Cécile Bacca, Martina Suty, and Elke Scheer — Universität Konstanz

We investigate lithographically fabricated breakjunctions of ferromagnetic metals. With the help of a three-point bending mechanism, the bridges can be opened and stabilized to a single-atom contact, broken to a vacuum-tunnel contact and closed again repeatedly at low temperatures (T≤ 4.2K). We observe steps in the conductance that are due to atomic rearrangements in the contact region [1] and calculate the preferred conductance value of a single Co atom with and without magnetic field. In addition we observe very high magnetoconductance effects up to 150% for single-atom or 500% for tunnel contacts in magnetic fields up to 5 T and perpendicular to the sample plane. We analyze the magnetoconductance as a function of the symmetry of the contact and of the free-standing bridge length. We developed a sample preparation method for samples the leads of which are made up of different materials than the contact itself and calculated [2] the magnetization state as a function of the geometry of the contact, the film thickness and its magnetic history. First results are presented.

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

[2] M.J. Donahue and D.J. Porter, OOMMF’s User Guide (see http://math.nist.gov/oommf)