Imaging excitations in magnetic thin film microstructures

We show how a photoemission electron microscope (PEEM) installed at a synchrotron can be used to image magnetic objects with very high spatial and temporal resolution. Sub-nanosecond magnetic field pulses are used to excite the fundamental magnetic modes of micron sized permalloy particles. The time evolution of the magnetization is imaged using a pump-probe technique where the magnetic contrast is given by X-ray magnetic circular dichroism (XMCD). Depending on the shape and size of the magnetic object we can observe modes related to either the homogenously magnetized domains, to the domain walls or to the vortex. All of these can be analyzed quantitatively yielding their frequencies, amplitudes and damping time constants. For objects with controlled defects we show that the magnetic vortex can be switched between defects using magnetic field pulses.