The spin structure of domain walls in constrictions down to 30nm is investigated both experimentally with electron holography and with simulations using a Heisenberg model. Symmetric and asymmetric transverse domain walls for different constriction sizes are observed, consistent with simulations. The experimentally observed asymmetric transverse walls can be further divided into tilted and buckled walls, the latter being an intermediate state just before the vortex nucleation. As the constriction width decreases, the domain wall width decreases faster than linearly, which leads to very narrow domain walls for narrow constrictions.

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