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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 13.39: Poster

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

Spin-polarized tunneling in FM/I/Al junctions based on ferromagnetic oxides — •Stefanie Wagner, Petra Majewski, Mitja Schonecke, Daniel Reisinger, Andreas Erb, Lambert Alff, Matthias Opel, and Rudolf Gross — Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meißner-Str. 8, 85748 Garching

Ferromagnet/insulator/superconductor (FM/I/SC) junctions are useful to determine the spin polarization of the charge carriers at the Fermi level in ferromagnetic materials [1]. Due to the Zeeman splitting in the quasiparticle density of states in superconductors, a non-zero spin polarization in the ferromagnet leads to an asymmetric tunnelling conductivity.
We have grown high quality thin films of La2/3Ba1/3MnO3 and Sr2CrWO6 on SrTiO3 substrates using UHV laser-MBE. The structural and magnetic properties of the films have been determined by x-ray diffraction and magnetization measurements. The insulating barriers (SiO2, Al2O3, SrTiO3) with a typical thickness of 2 nm have been deposited in-situ by UHV laser-MBE or electron beam evaporation. The surface morphology of both the ferromagnetic layer and the insulating barrier have been examined in-situ by atomic force microscopy. Finally, a thin superconducting layer of Al (Tc = 2.5K) is deposited by electron beam evaporation. After fabricating small tunnel junctions using optical lithography, we measure the conductivity across the junctions as a function of magnetic field at temperatures below 2 K.

[1] P.M. Tedrow and R. Meservey, Phys. Rev. Lett. 26, 191 (1971).

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