Micro magnetic dendritic domain structure in the demagnetized state of perpendicular magnetic ultrathin film: The effect of the width of the distribution of the energy barriers

We have used polar Kerr microscopy to study the magnetic domain structure in an ultrathin Au/Co(1 nm)/Au layer with perpendicular magnetic anisotropy. We present our demagnetization method of the sample. In the demagnetized state, we observed a dendritic domain structure. We theoretically calculated the lateral domain size in the demagnetized state by using two different models and we saw that the prefactor x=0.389 corresponds to the domain structure observed. We used polar magneto-optical Kerr effect magnetometry (PMOKE) to study the magnetization reversal and to extract an activation energy Ea in zero field and the width of the distribution of the energy barriers σw. We correlated the dendritic domain structure observed with the large value of σw.