Flux-closure-domain states and demagnetizing energy determination in sub-micron size magnetic dots

We used single-crystalline Fe dots self-assembled under UHV as a model system to discuss micromagnetic properties of sub-micron size magnetic dots and show what properties may or may not be scaled down from macroscopic samples. Landau and diamond states were identified by MFM and reproduced by simulations. These states are surprisingly well reproduced by the Van den Berg model despite the small dots' size. On the contrary, it is argued theoretically that the usual determination procedure of demagnetizing factors N-i's using initial susceptibility or the over-loop area underestimates the real values of N-i's in sub-micron size dots. This point is confirmed both experimentally and in simulations.