Nanoscale magnetic configurations of supported Fe nanoparticle assemblies studied by scanning electron microscopy with spin analysis

Microscopic magnetic behavior of supported nanoparticles is strongly correlated with their functionalities, especially in data storage and biological applications, but still needs to be clarified. We studied nanoscale magnetic configurations of Fe nanoparticle assemblies using scanning electron microscopy with polarization analysis. The flux closure domain configurations and the reduced magnetic correlation length $(\ensuremath{\sim}250\text{ }\text{nm})$, relative to the conventional thin films, are determined. Quantitative analysis indicates the magnetic interaction energy to be 80--99 meV, close to the magnetic dipolar coupling energy. These direct observations evidence the aforereported simulations and will be valuable for fabricating magnetic nanoparticle assemblies with the desired magnetic properties.