Formation of Magnetic Structure by Domain Wall Confinement in Nanoconstriction

We present here a study of exploiting Lorentz transmission electron microscopy to observe the magnetic structure in a nanobridge formed by confining a magnetic domain wall. The domain wall is nucleated in an elliptical pad by magnetization reversal and is driven to be pinned at the constriction to form a complex magnetic structure. High-resolution Lorentz microscopy shows that such a structure is composed by a mixture of S and C states of smooth rotation of the magnetization through the nanobridge rather than a conventional single wall as observed previously. This confinement contributes a domain wall resistance observed via anisotropic magnetoresistance presented previously. A serial transformation from S state to S/C mixture, to C state and finally to S state of the topology of the flux is evidently confirmed.