Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 15: Poster:ThinFilms(1-33),Transp.(34-49),ExchBias(50-56),
Spindynamics(57-70),Micro-nanostr.Mat.(71-82),
Particles/Clust.(83-88), Mag.Imag./Surface(89-96),
Spinelectronics(97-109), Theory/Micromag.(110-116),
Spinstruct/Phasetr.(117-128),Magn.Mat.(129-139),
Aniso.+Measuring(140-145), MolMag.(146-152),
MSMA(153-156)
MA 15.54: Poster
Dienstag, 27. März 2007, 15:00–19:00, Poster A
Magnetization reversal processes in patterned exchange biased NiO/Ni and Fe/CoO layers — •Pablo Aßhoff1, Florin Radu2, Katharina Theis-Bröhl1, and Hartmut Zabel1 — 1Department of Physics, Ruhr-University Bochum, D-44780 Bochum, Germany — 2BESSY GmbH, Albert-Einstein-Str. 15, D-12489 Berlin, Germany
We have investigated the magnetization reversal of arrays of exchange biased NiO/Ni and Fe/CoO squares with SQUID magnetometry. The edges of the squares were 0.5, 1.5 and 3.0 µm long. When the sizes of the structures are reduced, for the Fe/CoO structures both the exchange bias field and the slope of the hysteresis loops decrease continuously.
The NiO/Ni structures exhibit hysteresis loops typical of a vortex state. In a micromagnetic simulation of the system this special shape of the hysteresis loop was reproduced and a vortex state was observed. The exchange bias field behaves very unusual: for the arrays with NiO/Ni structures of 1.5 µm edge length the sign of the exchange bias field changes, as compared to the same continuous NiO/Ni layer. We attribute this to the interplay between shape and unidirectional anisotropy. In the exchange biased microstructures the unidirectional anisotropy causes a deformation of the whole hysteresis and not merely a uniform shift.
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