Imaging magnetization dynamics using photoemission electron microscopy

Time resolved X-PEEM imaging of magnetization reversal can be studied using a pump-probe arrangement, in which the pump is provided by a magnetic field-pulse synchronized with the x-ray pulse train. The figure shows a series of PEEM dichroism images at the Ni L3 edge (852.7 eV) taken from NiFe rectangles grown on top of high-bandwidth coplanar waveguides, which allows using the stray field induced by high speed current pulses as the pump. Images correspond to varying probe delay times, Δt, covering 3600 ps. In this sequence a pump field of ±10 Oe was reversed at ~1000 ps. The change from dark to light contrast indicates the full reversal of the NiFe dots. At intermediate times (1200-2100 ps), we see distinct domain patterns which clearly evolve with time. Although the field transition is only 150 ps long, there is significant ringing that is not damped quickly and the magnetic reversal takes over 1 ns. [J. Han and D. Keavney (APS), Y. Ji and A. Hoffmann (MSD, ANL) and R. Divan and L. Ocola (CNM, ANL)]

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