Magnetization dynamics in polycrystal line permalloy and epitaxial Co platelets observed by time-resolved photoemission electron microscopy

We studied the dynamic magnetization response in rectangular polycrystalline Permalloy and also epitaxial Co structures (lateral sizes comprised tens of microns at a thickness of tens of nanometers) during the action of a magnetic field pulse, using time-resolved X-ray photoemission electron microscopy with a time resolution of 10 ps. In the case of Permalloy platelets the restoring torque that is necessary for the stroboscopic image acquisition is provided by the Landau flux closure structure representing a minimum of the free energy. We investigated the dynamic response of 90 degrees Neel domain walls. The main results are: the maximum velocity of the domain wall is 1.5 x 10(4) m/s, the intrinsic frequency of the magnetization change in these structures is estimated to be several Gigahertz. For the case of epitaxial Co platelets grown on Mo(110) the magnetic uniaxial anisotropy with an easy axis along Mo[1 (1) over bar0] restores the homogeneous magnetization structure after each field pulse. We observed a rotation of the mean magnetization direction within the first 100 ps of the field pulse. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei