High spatial resolution quantitative micromagnetics (invited)

Abstract

Magnetization profiles at surfaces are observed with scanning electron microscopy with polarization analysis (SEMPA). This technique allows for quantitative analysis of the vector magnetization profile with 70 nm spatial resolution. Magnetization profiles in surface Néel walls which terminate bulk 180° Bloch walls at surfaces have been calculated by solving the micromagnetic equations using energy minimization. The micromagnetic calculations show that the surface Néel wall penetrates a distance from the surface comparable to a Bloch wall width and that the surface Néel wall width is at least twice the bulk Bloch wall width. The dependence of the domain wall magnetization on sample thickness is calculated for Fe, and model predictions of the wall widths that would be determined by transmission Lorentz microscopy are compared with the experimental results. The magnetic field outside of the sample, which gives rise to contrast with the Bitter technique and magnetic force microscopy (MFM), is a complicated superposition of contributions from both bulk and surface walls. Moreover, a strong mutual interaction between the sample and the MFM tip may alter the sample magnetization.