Regensburg 2004 – wissenschaftliches Programm
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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 13.93: Poster
Dienstag, 9. März 2004, 15:00–19:00, Bereich A
Transport Properties of Magnetite-Nb:SrTiO3 Interfaces — •M. Ziese, U. Köhler, R. Höhne, A. Bollero, and P. Esquinazi — Division of Superconductivity and Magnetism, University of Leipzig, Linnéstrasse 5, 04103 Leipzig.
The magnetotransport properties of contacts between magnetite and Nb-doped SrTiO3 were studied. Magnetite films were deposited on metallic Nb(0.1%):SrTiO3 single crystal substrates by pulsed laser deposition. During deposition the substrate temperature was 430∘C and oxygen partial pressure 10−5 mbar. At these conditions epitaxial films with Verwey temperatures of 115 K were obtained. The magnetotransport properties at the interface were investigated by four probe measurements in current-perpendicular-to-plane configuration by recording current (I)–voltage (V) characteristics at various temperatures (60 K ≤ T ≤ 300 K) and magnetic fields (µ0H ≤ 6 T). The I-V-characteristics showed rectifying behaviour, especially below the Verwey transition. The data could be successfully analyzed within a Schottky-barrier model; below the Verwey transition an energy barrier of about 0.1 eV was extracted, which vanished above the transition. The ideality factor n increases from a value near unity below 80 K to n ∼ 4 above 135 K. The magnetoresistance of this interface depends strongly on the bias voltage. When analyzed within thermionic emission theory taking a barrier potential shift due to the Zeeman effect into account, a spin polarization of −60% was obtained.