Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 19: Spin Dynamics / Spin Torque I

MA 19.3: Vortrag

Mittwoch, 27. Februar 2008, 14:30–14:45, EB 301

Spin-torque driven excitations in strongly antiferromagnetically coupled Co/Cu/Co bilayer nanostructures. — •Eva Maynicke¹, Marc Weidenbach¹, Nicolas Müsgens¹, Coen Smits¹, Bernd Beschoten¹, Matthias Bückins², Joachim Mayer², and Gernot Güntherot¹ — ¹II Physikalisches Institut A, RWTH Aachen, 52056 Aachen, and Virtual Institute for Spinelectronics (VISel) — ²Gemeinschaftslabor für Elektronenmikroskopie, RWTH Aachen, 52065 Aachen

We investigate the current-induced switching behaviour and high frequency dynamics in MBE grown Co/Cu/Co nanopillars with lateral dimensions below 100 nm by means of transport and microwave probes at room temperature.

In contrast to previous studies we observe a two-step magnetic reversal in field-sweep measurements at low current densities with an intermediate stable state between parallel and antiparallel alignment. The intermediate state is most stable in samples with strong antiferromagnetic coupling between both Co layers as tested by systematic variations of the Cu spacer layer thickness.

Near the critical field for magnetic switching into this intermediate state we observe pronounced dips in the differential resistance at negative currents. In this regime we detect microwave emission with broad spectral features extending from 50 MHz to 4 GHz. Surprisingly, there is no frequency shift with current or magnetic field.

Work supported by DFG through SPP1133.