Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 26: Exchange Bias
MA 26.13: Vortrag
Donnerstag, 29. März 2007, 18:15–18:30, H10
Size dependent scaling of perpendicular exchange bias in nanostructures — •Ildico Guhr1, Olav Hellwig2, Gregory Malinowski3, Sebastiaan van Dijken3, and Manfred Albrecht1 — 1University of Konstanz, Dept. of Physics, Konstanz, Germany — 2Hitachi San Jose Research Center, HGST, USA — 3SFI Trinity Nanoscience Laboratory, Trinity College, Dublin, Ireland
A magnetic nanopattern created by depositing Co/Pd or Co/Pt multilayers onto 2D arrays of self-assembled nanoparticles [1] will be introduced. The magnetic nanostructures formed on top of the particles are in a magnetically exchange-isolated quasi-single-domain state. This nanoscale system is quite distinct from the classical geometries. Here the deposited film is extended over a wide region of the sphere and thus shows substantial curvature. The film thickness varies and so do the intrinsic magnetic properties most notable the magneto-crystalline anisotropy [2]. This magnetic nanopattern is used to study the size-dependent scaling of exchange bias in nanostructures. [Pd/Co]-CoO and [Pt/Co]-IrMn layers with perpendicular magnetic anisotropy were deposited onto different arrays of monodisperse PS nanospheres with a diameter ranging from 58 to 320 nm. Below the blocking temperature we find for both systems a strong increase of the exchange bias field compared to continuous films. Interestingly, the exchange bias field increases drastically with decreasing particle size and shows a strong dependence on the applied cooling fields and training.
[1] M. Albrecht et al., Nature Material 4, (2005) 203.
[2] T. Ulbrich et al., Phys. Rev. Lett. 96, (2006) 077202.