Dresden 2003 – scientific programme
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MA: Magnetismus
MA 14: Poster: Schichten(1-31), Spinabh.Trsp.(32-47), Exch.Bias(48-54), Spindyn.(55-64), Mikromag.(65-76), Partikel(77-88), Oflmag.(89-92), Spinelektr.(93-98), Elektr.Theo.(99-103), Mikromag+PhasÜ+Aniso.(104-122), MagnMat.(123-134), Messm+Mol-Mag.(135-139), Kondo(140-151)
MA 14.71: Poster
Tuesday, March 25, 2003, 15:15–19:15, Zelt
Spin wave excitations in epitaxial Fe nanostructures on GaAs(001) — •Wolfgang Kipferl, Martin Dumm, Michael Rahm und Günther Bayreuther — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg
Thermal spin excitations in confined ferromagnetic structures become increasingly important, e.g. because they reduce the tunnel-magnetoresistance in highly integrated magnetic memories and the stability of stored information. Here, the effect of lateral confinement on the temperature dependence of magnetization in ultrathin films was studied. Epitaxial Fe films were grown on GaAs(001) by molecular beam epitaxy. Dot arrays with several million dots of well defined circular shape (diameter 100 - 500 nm) were fabricated by electron beam lithography and lift-off technique. The magnetic properties of the samples were investigated by SQUID magnetometry between 10 and 350 K. All films have an in-plane uniaxial magnetic anisotropy with the easy axis along [110] which is fully conserved during patterning. The temperature dependence of the spontaneous magnetization for T < 0.5 TC can be well described by Bloch’s law, M(T) = M(0) · (1 − B · T3/2), for all samples. With decreasing dot diameter the spin wave parameter B increases significantly compared to the extended film. The enhancement of spin wave excitations with decreasing film thickness and lateral dimension is discussed in comparison to existing theories and model simulations.