Domain structures and switching mechanisms in patterned magnetic elements

Domain formation and magnetisation reversal in lithographically fabricated magnetic elements 100-300 nm wide and 1.5-4.0 mu m long have been investigated using Lorentz imaging and finite element micromagnetics. The numerical integration of the Gilbert equation of motion resolves magnetisation processes in time and in space. The calculated domain patterns are in qualitative agreement with magnetic images obtained from Lorentz electron microscopy. NiFe elements show a small scale domain structure in the remanent state which may be attributed to a transverse anisotropy. In bars with one pointed end, the formation of the domains starts from the flat ends. Narrow elements with a width smaller than 200 nm remain in a nearly single domain state. Pointed ends suppress the formation of domains in NiFe elements and increase the switching field by about a factor of two in Co elements.