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 E a in zero field and the width of the distribution of the energy barriers σ w . We correlated the dendritic domain structure observed with the large value of σ w .