Dresden 2003 – scientific programme
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MA: Magnetismus
MA 25: Spinabh
ängige Transportph
änomene I
MA 25.3: Talk
Thursday, March 27, 2003, 15:45–16:00, HSZ/04
Brillouin light scattering on magnetic tunnel junctions — •Martin Weides, Simon Stein, Daniel Bürgler, Hermann Kohlstedt, and Peter Grünberg — Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich
There is an ongoing debate concerning the bias dependence of the tunneling magneto resistance (TMR) effect. The decrease of the magnetoresistance with increasing bias voltage is either attributed to defects in the tunnel barrier and/or to magnon scattering at the electrode-barrier interfaces. The creation/annihilation of a magnon is due to electron spin flip processes, reduces the electron spin polarization at the interface, and thereby the TMR.
Magnon excitations in thin ferromagnetic films are detectable by Brillouin light scattering (BLS). We use a Nd:YAG laser (532nm, 150 W, 40 µm diameter) in a 45∘ backscattering geometry and a Tandem Fabry Perot interferometer. The aim of this work is to study the bias dependence of magnetic tunnel junctions while simultaneously measuring the BLS spectrum. First results on magnetic tunnel junctions with areas between 100 µm2 and 30 000 µm2 and a junction area resistance (R· A) of 100 kΩµm2 are presented. Details of the fabrication and measuring process will be explained.
The results are discussed in the frame work of magnon creation by the sample current and bias voltage.