Regensburg 2004 – scientific programme

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MA: Magnetismus

MA 13: Poster:Schichten(1-23),Spinabh.Trsp(24-41),Exch.Bias(42-56),Spindyn.(57-67),Mikromag.(68-76),Partikel(77-90),Spinelektr.(91-97),Elektr.Theo.(98-99),Mikromag+PhasÜ+Aniso.(100-105),Magn.Mat.(106-118),Messmethod.(119-121),Obflm.+Abbverf.(122-123)

MA 13.86: Poster

Tuesday, March 9, 2004, 15:00–19:00, Bereich A

Coulomb-Blockade and spin-dependent tunneling in cobalt nanoparticles — •Herbert Graf, Johann Vancea, Christian Back, and Horst Hoffmann — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany

We report on the observation of the Coulomb blockade at room temperature and 77 K in cobalt nanoparticles with sizes ranging between 2 and 5 nm. The Co particle-arrays are contacted via in-plane point contacts. The sharp point contacts have a separation between 10 and 70 nm. Prior to the deposition of the Co particles, we evaporate a thin 1 - 3 nm thick layer of AlOx onto the gap structures. The particles are then grown onto the AlOx layer at temperatures between 300 K and 500 K. The electrical measurements are performed inside the same UHV apparatus. Magnetoresistance measurement loops with an in-situ electro-magnet show magnetoresistance values of a few percent at 77 K. An enhanced magnetoresistance above the threshold voltage of the particle array was observed. We suppose that this enhancement is related to the Coulomb blockade effect.