Dresden 2006 – wissenschaftliches Programm

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SYMS: Magnetic Switching

SYMS 1: Magnetic Switching I

SYMS 1.2: Hauptvortrag

Montag, 27. März 2006, 15:45–16:15, HSZ 04

Spin-torque effects in single-crystalline Fe nanomagnets and nanopillars — •Daniel E. Bürgler, Henning Dassow, Ronald Lehndorff, Matthias Buchmeier, Peter A. Grünberg, and Claus M. Schneider — Institut für Festkörperforschung und cni - Center of Nanoelectronic Systems for Information Technology, Forschungszentrum Jülich GmbH

We report on current-induced magnetization switching (CIMS) and microwave excitations in single-crystalline Fe nanomagnets and nanopillars. Fe(14)/Cr(0.9)/Fe(10)/Ag(6)/Fe(2) [thicknesses in nm] multilayers are prepared by molecular beam epitaxy. The middle Fe layer is magnetically hardened due to AF interlayer coupling across the Cr spacer. The topmost Fe layer is decoupled and acts as free layer. Nanomagnets and nanopillars with diameters of about 150 nm are patterned by optical and e-beam lithography. The CPP-GMR is 2.6% at RT and 5.6% at 4 K. Clearly different GMR curves for the field along the easy and hard axes of Fe(001) indicate the single-crystalline nature of the nanostructures. Hysteretic CIMS occurs at current densities larger than 2×10⁷ A/cm². The critical current density and the switching behavior are different for the field applied along easy and hard axes. In nanopillars, CIMS appears for both current polarities and is related to the switching of the top or middle Fe layer, respectively, and to the different spin scattering asymmetries of Fe/Cr and Fe/Ag interfaces. High-frequency spectroscopy reveals magnetic GHz excitations in the nanomagnets with a rich dependence of the excitation frequency on the DC current, field strength and direction, again with clearly different easy and hard axis behaviors.