ES-02 Analysis of magnetic relaxation with pre-existing nucleation sites based on the FatuzzoLabrune model D. QUACH1, D. HANDOKO1, S. LEE1, J. SHIM1, T. PHAN1, D. KIM1, D. PHAM2, K. LEE3, J. JEONG3, D. NGO4 Department of Physics, Chungbuk National University, Cheongju, Korea; Faculty of Engineering Physics and Nanotechnology, University of Engineering and Technology, Vietnam National University, Hanoi, Viet Nam; Department of Material Science and Engineering and Graduate School of Energy Science and Technology, Chungnam National University, Daejeon, Korea; Department of Micro- and Nanotechnology, Technical University of Denmark, Kgs Lyngby 2800, Denmark Time-resolved magnetic domain patterns of (Co/Pt) and (CoFeB/Pd) multilayers with perpendicular magnetic anisotropy are observed by means of magneto-optical microscopy, from which magnetic relaxation curves are determined for Interestingly, it has been observed that the relaxation processes not only from the saturated state, but also with pre-existing domains, are well explained based on the Fatuzzo-Labrune model [1, 2] Full details of the relaxation behavior and subsequent microscopic domain patterns evolving from the pre-existing nucleation sites originated from the sub-structured magnetic domains are discussed It has been well known that the Fatuzzo-Labrune model is applicable in explaining magnetic relaxation processes involved with a thermally activated magnetization reversal in various magnetic thin films [3, 4] According to the model, the magnetic relaxation is quantied by a reversal parameter k = v/Rrc, where v is the domain wall velocity, R the nucleation rate, and rc the initial domain radius The shape of the curve and the value of k reflect a competition between domain wall motion and domain nucleation during the magnetic relaxation process For k >> 1, the magnetization reversal mechanism is known to be dominated by domain wall propagation and the curve has a so-called S-shaped one, while, for k