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 15.53: Poster
Dienstag, 27. März 2007, 15:00–19:00, Poster A
Antiferromagnetic thickness dependence of exchange bias — •Shrawan Mishra, Florin Radu, Bernd Heitkamp, Jaime Sanchez-Barriga, Hermann Dürr, and Wolfgang Eberhardt — BESSY GmbH, Albert-Einstein Strasse 15, D-12489,
We have studied systematically the dependence of exchange bias and coercive fields as function of antiferromagnetic (AF) layer thickness. A series of Si(100)/SiO2/Cu(5 nm)/Ni81Fe19(20 nm)/Ir20Mn80(x)/Cu(2.5 nm) bilayers were grown at MAGSSY magnetron sputtering system of BESSY. For each AF thickness the coercive and exchange bias fields were extracted from the azimuthal dependent hysteresis loops measured by Magneto Optical Kerr Effect(MOKE). It is observed that at the critical thickness for the AF layer, the EB bias field exhibits a sudden jump increasing monotonically as a function of the AF thickness towards a saturation value. The coercivity in this region is equal to the coercive field of the ferromagnetic layer measured separately. On the other hand, below the critical AF thickness the exchange bias vanishes with effective enhanced coercivity. The coercive field is maximum close to the critical AF thickness and decreases with decreasing the AF layer thickness. Therefore, at room temperature the phase diagram for exchange bias and coercivity can be described using a Meiklejohn and Bean mechanism for exchange bias. This is further demonstrated by comparing numerical simulations with experimental data.