The switching behavior of submicron circular Permalloy nanomagnets has been investigated. Electron holography provides a magnetic resolution of down to 10 nm. This allows us to observe in detail the switching and to measure the induction within single nanodots with diameters down to 150 nm at a thickness of 6 nm. Particles of these dimensions show a single domain state during the whole switching process which takes place at external fields of only a few $100\mathrm{A}/\mathrm{m}$. For larger or thicker particles the magnetization reversal runs via the formation of a C state or an intermediate vortex state.

• Received 14 June 2004

DOI:https://doi.org/10.1103/PhysRevLett.94.077202