Dresden 2009 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 7: Spin-Dynamics/ Spin-Torque II

MA 7.7: Vortrag

Montag, 23. März 2009, 16:45–17:00, HSZ 04

Spin transfer torque in pillar arrays investigated by ferromagnetic resonance — •Oliver Posth, Günter Dumpich, and Jürgen Lindner — Fachbereich Physik, Experimentalphysik, AG Farle, Universität Duisburg-Essen, 47048 Duisburg, Germany

It is well known from other studies that a spin polarized current in a ferromagnet exerts a torque on the magnetic moments by spin-momentum transfer. This current can be used to switch the magnetization of one ferromagnetic layer in a ferromagnetic metal / nonmagnetic metal / ferromagnetic metal spin valve device. We investigate the influence of the spin polarized current on the damping in the ferromagnetic layers of the pillar structures directly by means of ferromagnetic resonance (FMR). The pillars are prepared and electrically contacted by high-resolution electron beam lithography (HR-EBL) and electron beam evaporation in a multi-step process. The FMR measurements are carried out on a pillar array, in which all pillars are connected in series, so that we are able to increase the current density to a value being sufficient to observe the effect of the spin transfer torque. The temperature rise due to high current density is avoided by a cooling set-up. An influence of the spin torque effect on the intrinsic damping in the ferromagnet can be observed for in plane orientation as well for out of plane orientation of the magnetic field. The influence of the Oersted-field is estimated in addition. We further investigate the domain structure of the pillars in an applied field by means of micromagnetic calculations. This work is supported by the Deutsche Forschungsgemeinschaft within SFB 491.