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MA: Fachverband Magnetismus

MA 24: Spindynamics / Switching II

MA 24.10: Vortrag

Donnerstag, 29. März 2007, 12:30–12:45, H23

Ferromagnetic resonance study of the interlayer exchange coupled NiFe/Ru/NiFe films — •Mohamed Belmeguenai, Tobias Martin, Georg Woltersdorf, and Günther Bayreuther — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany

Ferromagnetic bilayers exchange coupled through a non-magnetic metallic layer are used in magnetic recording devices. Their dynamics at 1 to 10 GHz which present a fundamental limit to increasing data rates have been studied in this work. We used conventional ferromagnetic resonance (FMR) and vector network analyzer FMR to study the different excited dynamic modes in exchange coupled Si/Ta/NiFe(30 nm)/Ru(dRu)/NiFe(30 nm)/Ta films with variable Ru thicknesses dRu. The interlayer exchange coupling (IEC) constants are determined by VSM and MOKE. The dynamic measurements show the existence of an optic and an acoustic precession mode. Their resonance frequencies and therefore the IEC are found to oscillate as a function of dRu with a period of 8.5 Å. The frequency oscillations of the optic mode are coupling-dependent while those of the acoustic mode are indirectly related to coupling via the canting angle of the layer magnetizations. The FMR measurements carried out at 22 and 35 GHz revealed clearly different behaviors of the FMR linewidths as a function of dRu for the optic and acoustic modes and we observed perpendicular standing spin-waves. The FMR linewidth of the different excited modes increases with the microwave frequencies and typical damping constants of 0.0073 have been measured.