Berlin 2005 – scientific programme

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MA: Magnetismus

MA 8: Spindynamik I

MA 8.5: Talk

Friday, March 4, 2005, 16:15–16:30, TU H1028

Ferromagnetic resonance in magnetic microstructures studied using phase resolved Kerr microscopy — •Ingo Neudecker, Rainer Höllinger, Dieter Weiss, and Christian H. Back — Institut fuer Experimentelle und Angewandte Physik, Universitaet Regensburg, Universitaetsstrasse 31, 93040 Regensburg

We present a technique to investigate the eigenmode spectrum with a spatial resolution of about 300 nm using phase resolved magneto optic Kerr effect.

Instead of exciting the magnetic elements by a short magnetic field pulse containing a broad frequency spectrum we use a sinusoidal magnetic field to excite only a single mode of the system. The sinusoidal excitation is phase locked to the repetition rate of 80 MHz of our Ti:Sapphire laser system. Due to the bandwidth of the signal generator we are able to investigate the eigenmode spectrum from 80 MHz up to 20 GHz in 80 MHz intervals, limited in principle only by the spatial resolution of the Kerr setup.

The magnetic system investigated are 4 micron diameter permalloy disks with 20 nm thickness defined by electron beam lithography on top of a lithographically fabricated microwave guide.

The in plane high frequency field excites symmetry breaking azimuthal eigenmodes, which we were able to resolve up to the third order. Additionally we identified the spatially resolved evolution of the main mode as a function of a static external bias field. A comparison of the results to Network Analyzer - ferromagnetic resonance measurements and micromagnetic simulations show excellent agreement.