Dresden 2003 – scientific programme

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MA: Magnetismus

MA 14: Poster: Schichten(1-31), Spinabh.Trsp.(32-47), Exch.Bias(48-54), Spindyn.(55-64), Mikromag.(65-76), Partikel(77-88), Oflmag.(89-92), Spinelektr.(93-98), Elektr.Theo.(99-103), Mikromag+PhasÜ+Aniso.(104-122), MagnMat.(123-134), Messm+Mol-Mag.(135-139), Kondo(140-151)

MA 14.77: Poster

Tuesday, March 25, 2003, 15:15–19:15, Zelt

Single-electron and spin-dependent tunneling in cobalt nanoparticles — •Herbert Graf, Johann Vancea, Christian Back, and Horst Hoffmann — NWF II, Universität Regensburg, Universitätsstr. 31, 93040 Regensburg

We report on the observation of the Coulomb blockade with Coulomb staircases at room temperature in cobalt nanoparticles, with sizes ranging between 2 and 4 nm. A monolayer of these particles is supported by a thin 1 - 2 nm thick Al2O3 film, deposited on a smooth Au(111) surface. The local electrical-transport on isolated Co clusters was investigated with a scanning tunneling microscope. The tunnel contact of the STM-tip allowed us to observe single-electron tunneling in the double barrier system STM-tip/Co/Al2O3/Au. Very high values for the Coulomb blockade of up to 1.0 V were reproducibly measured at room temperature on different particles with this setup.The current-voltage characteristics are well fitted by simulations based on the orthodox theory of single-electron tunneling. In a second step we measured the I-V characteristics of Co particle-arrays, contacted via in-plane point contacts. We observed a tunneling magnetoresistance of the order of 1% at room temperature at a magnetic field of 0.2 Tesla.